diff --git a/Source/NSGCString.m b/Source/NSGCString.m
index 7f746ad08..2c004f07c 100644
--- a/Source/NSGCString.m
+++ b/Source/NSGCString.m
@@ -696,8 +696,11 @@ static	IMP	msInitImp;	/* designated initialiser for mutable	*/
 		       options: (unsigned int)mask
 			 range: (NSRange)aRange
 {
-  Class	c = fastClass(aString);
+  Class	c;
 
+  if (aString == nil)
+    [NSException raise: NSInvalidArgumentException format: @"compare with nil"];
+  c = fastClass(aString);
   if (c == _fastCls._NSGString || c == _fastCls._NSGMutableString)
     return strCompCsUs(self, aString, mask, aRange);
   else if (c == _fastCls._NSGCString || c == _fastCls._NSGMutableCString
@@ -711,8 +714,11 @@ static	IMP	msInitImp;	/* designated initialiser for mutable	*/
 		  options: (unsigned int) mask
 		    range: (NSRange) aRange
 {
-  Class	c = fastClass(aString);
+  Class	c;
 
+  if (aString == nil)
+    [NSException raise: NSInvalidArgumentException format: @"range of nil"];
+  c = fastClass(aString);
   if (c == _fastCls._NSGString || c == _fastCls._NSGMutableString)
     return strRangeCsUs(self, aString, mask, aRange);
   else if (c == _fastCls._NSGCString || c == _fastCls._NSGMutableCString
diff --git a/Source/NSGString.m b/Source/NSGString.m
index f61486510..d5fcd17a0 100644
--- a/Source/NSGString.m
+++ b/Source/NSGString.m
@@ -430,8 +430,11 @@
 		       options: (unsigned int)mask
 			 range: (NSRange)aRange
 {
-  Class	c = fastClass(aString);
+  Class	c;
 
+  if (aString == nil)
+    [NSException raise: NSInvalidArgumentException format: @"compare with nil"];
+  c = fastClass(aString);
   if (c == _fastCls._NSGString || c == _fastCls._NSGMutableString)
     return strCompUsUs(self, aString, mask, aRange);
   else if (c == _fastCls._NSGCString || c == _fastCls._NSGMutableCString
@@ -445,8 +448,11 @@
 		  options: (unsigned int) mask
 		    range: (NSRange) aRange
 {
-  Class	c = fastClass(aString);
+  Class	c;
 
+  if (aString == nil)
+    [NSException raise: NSInvalidArgumentException format: @"range of nil"];
+  c = fastClass(aString);
   if (c == _fastCls._NSGString || c == _fastCls._NSGMutableString)
     return strRangeUsUs(self, aString, mask, aRange);
   else if (c == _fastCls._NSGCString || c == _fastCls._NSGMutableCString
diff --git a/Source/NSString.m b/Source/NSString.m
index e09fd81a0..01aff78a4 100644
--- a/Source/NSString.m
+++ b/Source/NSString.m
@@ -842,6 +842,8 @@ handle_printf_atsign (FILE *stream,
 		  options: (unsigned int) mask
 		    range: (NSRange) aRange
 {
+  if (aString == nil)
+    [NSException raise: NSInvalidArgumentException format: @"range of nil"];
   return strRangeNsNs(self, aString, mask, aRange);
 }
 
@@ -884,6 +886,8 @@ handle_printf_atsign (FILE *stream,
 		       options: (unsigned int)mask
 			 range: (NSRange)aRange
 {
+  if (aString == nil)
+    [NSException raise: NSInvalidArgumentException format: @"compare with nil"];
   return strCompNsNs(self, aString, mask, aRange);
 }