diff --git a/include/dsd.h b/include/dsd.h
index fb98555..00b9a77 100644
--- a/include/dsd.h
+++ b/include/dsd.h
@@ -1194,7 +1194,7 @@ void rtl_clean_queue();
 int ez_rs28_ess (int payload[96], int parity[168]); //ezpwd bridge for FME
 int ez_rs28_facch (int payload[156], int parity[114]); //ezpwd bridge for FME
 int ez_rs28_sacch (int payload[180], int parity[132]); //ezpwd bridge for FME
-int isch_lookup (unsigned long long int isch); //isch map lookup
+int isch_lookup (uint64_t isch); //isch map lookup
 int bd_bridge (int payload[196], uint8_t decoded[12]); //bridge to Michael Ossmann Block De-interleaver and 1/2 rate trellis decoder
 int crc16_lb_bridge (int payload[190], int len);
 int crc12_xb_bridge (int payload[190], int len);
diff --git a/src/ez.cpp b/src/ez.cpp
index c66de53..d508459 100644
--- a/src/ez.cpp
+++ b/src/ez.cpp
@@ -178,146 +178,166 @@ int ez_rs28_sacch (int payload[180], int parity[132])
   return (ec);
 }
 
-//I-ISCH Lookup section, borrowed from OP25
-std::map <std::string, int> isch_map;
+std::map <std::uint64_t, int> isch_map;
 void map_isch()
 {
-	isch_map["184229d461"] = 0;
-	isch_map["18761451f6"] = 1;
-	isch_map["181ae27e2f"] = 2;
-	isch_map["182edffbb8"] = 3;
-	isch_map["18df8a7510"] = 4;
-	isch_map["18ebb7f087"] = 5;
-	isch_map["188741df5e"] = 6;
-	isch_map["18b37c5ac9"] = 7;
-	isch_map["1146a44f13"] = 8;
-	isch_map["117299ca84"] = 9;
-	isch_map["111e6fe55d"] = 10;
-	isch_map["112a5260ca"] = 11;
-	isch_map["11db07ee62"] = 12;
-	isch_map["11ef3a6bf5"] = 13;
-	isch_map["1183cc442c"] = 14;
-	isch_map["11b7f1c1bb"] = 15;
-	isch_map["1a4a2e239e"] = 16;
-	isch_map["1a7e13a609"] = 17;
-	isch_map["1a12e589d0"] = 18;
-	isch_map["1a26d80c47"] = 19;
-	isch_map["1ad78d82ef"] = 20;
-	isch_map["1ae3b00778"] = 21;
-	isch_map["1a8f4628a1"] = 22;
-	isch_map["1abb7bad36"] = 23;
-	isch_map["134ea3b8ec"] = 24;
-	isch_map["137a9e3d7b"] = 25;
-	isch_map["13166812a2"] = 26;
-	isch_map["1322559735"] = 27;
-	isch_map["13d300199d"] = 28;
-	isch_map["13e73d9c0a"] = 29;
-	isch_map["138bcbb3d3"] = 30;
-	isch_map["13bff63644"] = 31;
-	isch_map["1442f705ef"] = 32;
-	isch_map["1476ca8078"] = 33;
-	isch_map["141a3cafa1"] = 34;
-	isch_map["142e012a36"] = 35;
-	isch_map["14df54a49e"] = 36;
-	isch_map["14eb692109"] = 37;
-	isch_map["14879f0ed0"] = 38;
-	isch_map["14b3a28b47"] = 39;
-	isch_map["1d467a9e9d"] = 40;
-	isch_map["1d72471b0a"] = 41;
-	isch_map["1d1eb134d3"] = 42;
-	isch_map["1d2a8cb144"] = 43;
-	isch_map["1ddbd93fec"] = 44;
-	isch_map["1defe4ba7b"] = 45;
-	isch_map["1d831295a2"] = 46;
-	isch_map["1db72f1035"] = 47;
-	isch_map["164af0f210"] = 48;
-	isch_map["167ecd7787"] = 49;
-	isch_map["16123b585e"] = 50;
-	isch_map["162606ddc9"] = 51;
-	isch_map["16d7535361"] = 52;
-	isch_map["16e36ed6f6"] = 53;
-	isch_map["168f98f92f"] = 54;
-	isch_map["16bba57cb8"] = 55;
-	isch_map["1f4e7d6962"] = 56;
-	isch_map["1f7a40ecf5"] = 57;
-	isch_map["1f16b6c32c"] = 58;
-	isch_map["1f228b46bb"] = 59;
-	isch_map["1fd3dec813"] = 60;
-	isch_map["1fe7e34d84"] = 61;
-	isch_map["1f8b15625d"] = 62;
-	isch_map["1fbf28e7ca"] = 63;
-	isch_map["84d62c339"] = 64;
-	isch_map["8795f46ae"] = 65;
-	isch_map["815a96977"] = 66;
-	isch_map["82194ece0"] = 67;
-	isch_map["8d0c16248"] = 68;
-	isch_map["8e4fce7df"] = 69;
-	isch_map["8880ac806"] = 70;
-	isch_map["8bc374d91"] = 71;
-	isch_map["149ef584b"] = 72;
-	isch_map["17dd2dddc"] = 73;
-	isch_map["11124f205"] = 74;
-	isch_map["125197792"] = 75;
-	isch_map["1d44cf93a"] = 76;
-	isch_map["1e0717cad"] = 77;
-	isch_map["18c875374"] = 78;
-	isch_map["1b8bad6e3"] = 79;
-	isch_map["a456534c6"] = 80;
-	isch_map["a7158b151"] = 81;
-	isch_map["a1dae9e88"] = 82;
-	isch_map["a29931b1f"] = 83;
-	isch_map["ad8c695b7"] = 84;
-	isch_map["aecfb1020"] = 85;
-	isch_map["a800d3ff9"] = 86;
-	isch_map["ab430ba6e"] = 87;
-	isch_map["341e8afb4"] = 88;
-	isch_map["375d52a23"] = 89;
-	isch_map["3192305fa"] = 90;
-	isch_map["32d1e806d"] = 91;
-	isch_map["3dc4b0ec5"] = 92;
-	isch_map["3e8768b52"] = 93;
-	isch_map["38480a48b"] = 94;
-	isch_map["3b0bd211c"] = 95;
-	isch_map["44dbc12b7"] = 96;
-	isch_map["479819720"] = 97;
-	isch_map["41577b8f9"] = 98;
-	isch_map["4214a3d6e"] = 99;
-	isch_map["4d01fb3c6"] = 100;
-	isch_map["4e4223651"] = 101;
-	isch_map["488d41988"] = 102;
-	isch_map["4bce99c1f"] = 103;
-	isch_map["d493189c5"] = 104;
-	isch_map["d7d0c0c52"] = 105;
-	isch_map["d11fa238b"] = 106;
-	isch_map["d25c7a61c"] = 107;
-	isch_map["dd49228b4"] = 108;
-	isch_map["de0afad23"] = 109;
-	isch_map["d8c5982fa"] = 110;
-	isch_map["db864076d"] = 111;
-	isch_map["645bbe548"] = 112;
-	isch_map["6718660df"] = 113;
-	isch_map["61d704f06"] = 114;
-	isch_map["6294dca91"] = 115;
-	isch_map["6d8184439"] = 116;
-	isch_map["6ec25c1ae"] = 117;
-	isch_map["680d3ee77"] = 118;
-	isch_map["6b4ee6be0"] = 119;
-	isch_map["f41367e3a"] = 120;
-	isch_map["f750bfbad"] = 121;
-	isch_map["f19fdd474"] = 122;
-	isch_map["f2dc051e3"] = 123;
-	isch_map["fdc95df4b"] = 124;
-	isch_map["fe8a85adc"] = 125;
-	isch_map["f845e7505"] = 126;
-	isch_map["fb063f092"] = 127;
+	isch_map[0x184229d461ULL] = 0;
+	isch_map[0x18761451f6ULL] = 1;
+	isch_map[0x181ae27e2fULL] = 2;
+	isch_map[0x182edffbb8ULL] = 3;
+	isch_map[0x18df8a7510ULL] = 4;
+	isch_map[0x18ebb7f087ULL] = 5;
+	isch_map[0x188741df5eULL] = 6;
+	isch_map[0x18b37c5ac9ULL] = 7;
+	isch_map[0x1146a44f13ULL] = 8;
+	isch_map[0x117299ca84ULL] = 9;
+	isch_map[0x111e6fe55dULL] = 10;
+	isch_map[0x112a5260caULL] = 11;
+	isch_map[0x11db07ee62ULL] = 12;
+	isch_map[0x11ef3a6bf5ULL] = 13;
+	isch_map[0x1183cc442cULL] = 14;
+	isch_map[0x11b7f1c1bbULL] = 15;
+	isch_map[0x1a4a2e239eULL] = 16;
+	isch_map[0x1a7e13a609ULL] = 17;
+	isch_map[0x1a12e589d0ULL] = 18;
+	isch_map[0x1a26d80c47ULL] = 19;
+	isch_map[0x1ad78d82efULL] = 20;
+	isch_map[0x1ae3b00778ULL] = 21;
+	isch_map[0x1a8f4628a1ULL] = 22;
+	isch_map[0x1abb7bad36ULL] = 23;
+	isch_map[0x134ea3b8ecULL] = 24;
+	isch_map[0x137a9e3d7bULL] = 25;
+	isch_map[0x13166812a2ULL] = 26;
+	isch_map[0x1322559735ULL] = 27;
+	isch_map[0x13d300199dULL] = 28;
+	isch_map[0x13e73d9c0aULL] = 29;
+	isch_map[0x138bcbb3d3ULL] = 30;
+	isch_map[0x13bff63644ULL] = 31;
+	isch_map[0x1442f705efULL] = 32;
+	isch_map[0x1476ca8078ULL] = 33;
+	isch_map[0x141a3cafa1ULL] = 34;
+	isch_map[0x142e012a36ULL] = 35;
+	isch_map[0x14df54a49eULL] = 36;
+	isch_map[0x14eb692109ULL] = 37;
+	isch_map[0x14879f0ed0ULL] = 38;
+	isch_map[0x14b3a28b47ULL] = 39;
+	isch_map[0x1d467a9e9dULL] = 40;
+	isch_map[0x1d72471b0aULL] = 41;
+	isch_map[0x1d1eb134d3ULL] = 42;
+	isch_map[0x1d2a8cb144ULL] = 43;
+	isch_map[0x1ddbd93fecULL] = 44;
+	isch_map[0x1defe4ba7bULL] = 45;
+	isch_map[0x1d831295a2ULL] = 46;
+	isch_map[0x1db72f1035ULL] = 47;
+	isch_map[0x164af0f210ULL] = 48;
+	isch_map[0x167ecd7787ULL] = 49;
+	isch_map[0x16123b585eULL] = 50;
+	isch_map[0x162606ddc9ULL] = 51;
+	isch_map[0x16d7535361ULL] = 52;
+	isch_map[0x16e36ed6f6ULL] = 53;
+	isch_map[0x168f98f92fULL] = 54;
+	isch_map[0x16bba57cb8ULL] = 55;
+	isch_map[0x1f4e7d6962ULL] = 56;
+	isch_map[0x1f7a40ecf5ULL] = 57;
+	isch_map[0x1f16b6c32cULL] = 58;
+	isch_map[0x1f228b46bbULL] = 59;
+	isch_map[0x1fd3dec813ULL] = 60;
+	isch_map[0x1fe7e34d84ULL] = 61;
+	isch_map[0x1f8b15625dULL] = 62;
+	isch_map[0x1fbf28e7caULL] = 63;
+	isch_map[0x084d62c339ULL] = 64;
+	isch_map[0x08795f46aeULL] = 65;
+	isch_map[0x0815a96977ULL] = 66;
+	isch_map[0x082194ece0ULL] = 67;
+	isch_map[0x08d0c16248ULL] = 68;
+	isch_map[0x08e4fce7dfULL] = 69;
+	isch_map[0x08880ac806ULL] = 70;
+	isch_map[0x08bc374d91ULL] = 71;
+	isch_map[0x0149ef584bULL] = 72;
+	isch_map[0x017dd2dddcULL] = 73;
+	isch_map[0x011124f205ULL] = 74;
+	isch_map[0x0125197792ULL] = 75;
+	isch_map[0x01d44cf93aULL] = 76;
+	isch_map[0x01e0717cadULL] = 77;
+	isch_map[0x018c875374ULL] = 78;
+	isch_map[0x01b8bad6e3ULL] = 79;
+	isch_map[0x0a456534c6ULL] = 80;
+	isch_map[0x0a7158b151ULL] = 81;
+	isch_map[0x0a1dae9e88ULL] = 82;
+	isch_map[0x0a29931b1fULL] = 83;
+	isch_map[0x0ad8c695b7ULL] = 84;
+	isch_map[0x0aecfb1020ULL] = 85;
+	isch_map[0x0a800d3ff9ULL] = 86;
+	isch_map[0x0ab430ba6eULL] = 87;
+	isch_map[0x0341e8afb4ULL] = 88;
+	isch_map[0x0375d52a23ULL] = 89;
+	isch_map[0x03192305faULL] = 90;
+	isch_map[0x032d1e806dULL] = 91;
+	isch_map[0x03dc4b0ec5ULL] = 92;
+	isch_map[0x03e8768b52ULL] = 93;
+	isch_map[0x038480a48bULL] = 94;
+	isch_map[0x03b0bd211cULL] = 95;
+	isch_map[0x044dbc12b7ULL] = 96;
+	isch_map[0x0479819720ULL] = 97;
+	isch_map[0x041577b8f9ULL] = 98;
+	isch_map[0x04214a3d6eULL] = 99;
+	isch_map[0x04d01fb3c6ULL] = 100;
+	isch_map[0x04e4223651ULL] = 101;
+	isch_map[0x0488d41988ULL] = 102;
+	isch_map[0x04bce99c1fULL] = 103;
+	isch_map[0x0d493189c5ULL] = 104;
+	isch_map[0x0d7d0c0c52ULL] = 105;
+	isch_map[0x0d11fa238bULL] = 106;
+	isch_map[0x0d25c7a61cULL] = 107;
+	isch_map[0x0dd49228b4ULL] = 108;
+	isch_map[0x0de0afad23ULL] = 109;
+	isch_map[0x0d8c5982faULL] = 110;
+	isch_map[0x0db864076dULL] = 111;
+	isch_map[0x0645bbe548ULL] = 112;
+	isch_map[0x06718660dfULL] = 113;
+	isch_map[0x061d704f06ULL] = 114;
+	isch_map[0x06294dca91ULL] = 115;
+	isch_map[0x06d8184439ULL] = 116;
+	isch_map[0x06ec25c1aeULL] = 117;
+	isch_map[0x0680d3ee77ULL] = 118;
+	isch_map[0x06b4ee6be0ULL] = 119;
+	isch_map[0x0f41367e3aULL] = 120;
+	isch_map[0x0f750bfbadULL] = 121;
+	isch_map[0x0f19fdd474ULL] = 122;
+	isch_map[0x0f2dc051e3ULL] = 123;
+	isch_map[0x0fdc95df4bULL] = 124;
+	isch_map[0x0fe8a85adcULL] = 125;
+	isch_map[0x0f845e7505ULL] = 126;
+	isch_map[0x0fb063f092ULL] = 127;
+	isch_map[0x575d57f7ffULL] =  -2; // S-ISCH
 }
 
-int isch_lookup (unsigned long long int isch)
+//I-ISCH Lookup, borrowed from OP25 (now w/ error correction)
+int isch_lookup (uint64_t isch)
 {
-  map_isch(); //initialize the lookup map
-  char s[64];
-  int decoded = -2; //initialize lookup to an invalid number
-  sprintf(s, "%llx", isch);
-  decoded = isch_map[s];
-  return(decoded);
-}
+	map_isch(); //initialize the lookup map
+	int decoded = -2;
+
+	// Must contain bit errors if no exact match, so
+	// look for codeword with smallest hamming distance
+	if (isch_map.find(isch) == isch_map.end())
+	{
+		int popct, popmin = 40;
+		for (auto it = isch_map.begin(); it != isch_map.end(); ++it)
+		{
+			popct = __builtin_popcountll(isch ^ it->first);
+			// Encoding is (40, 9, 16) which can correct at most 7 bit-errors
+			if ((popct <= 7) && (popct < popmin))
+			{
+					decoded = it->second;
+					popmin = popct;
+			}
+		}
+	return decoded;
+	}
+	else  // No errors, so simply return the matching value
+		decoded = isch_map[isch];
+		
+	return decoded;
+
+}
\ No newline at end of file
diff --git a/src/p25p2_frame.c b/src/p25p2_frame.c
index bf1af3d..c044237 100644
--- a/src/p25p2_frame.c
+++ b/src/p25p2_frame.c
@@ -75,7 +75,7 @@ int dibit = 0;
 int vc_counter = 0;
 int framing_counter = 0;
 
-unsigned long long int isch = 0;
+uint64_t isch = 0;
 int isch_decoded = -1;
 int p2_duid[8] = {0};
 int16_t duid_decoded = 0;