diff --git a/src/deh_soc.c b/src/deh_soc.c
index 9e3c2f242..ecf930bd9 100644
--- a/src/deh_soc.c
+++ b/src/deh_soc.c
@@ -3307,7 +3307,7 @@ static void readcondition(UINT8 set, UINT32 id, char *word2)
 		else
 			re = atoi(params[1]);
 
-		if (re < 0 || re >= NUMMAPS)
+		if (re <= 0 || re > NUMMAPS)
 		{
 			deh_warning("Level number %d out of range (1 - %d)", re, NUMMAPS);
 			return;
@@ -3327,7 +3327,7 @@ static void readcondition(UINT8 set, UINT32 id, char *word2)
 		else
 			x1 = (INT16)atoi(params[1]);
 
-		if (x1 < 0 || x1 >= NUMMAPS)
+		if (x1 <= 0 || x1 > NUMMAPS)
 		{
 			deh_warning("Level number %d out of range (1 - %d)", re, NUMMAPS);
 			return;
@@ -3362,7 +3362,7 @@ static void readcondition(UINT8 set, UINT32 id, char *word2)
 		else
 			x1 = (INT16)atoi(params[1]);
 
-		if (x1 < 0 || x1 >= NUMMAPS)
+		if (x1 <= 0 || x1 > NUMMAPS)
 		{
 			deh_warning("Level number %d out of range (1 - %d)", re, NUMMAPS);
 			return;