diff --git a/ChangeLog b/ChangeLog
index 37831f161..7c47c6a86 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,9 @@
+2006-12-05  Richard Frith-Macdonald <rfm@gnu.org>
+
+	* NSURL.m: Check for missing scheme and return nil.
+	* NSString.m: Check for character conversion failure when
+	getting a CString.
+
 2006-11-30  Richard Frith-Macdonald <rfm@gnu.org>
 
 	* Source/GSHTTPURLHandle.m: Limit size of handle cache to 16 to
diff --git a/Source/NSString.m b/Source/NSString.m
index 22e6e9a97..ef955875a 100644
--- a/Source/NSString.m
+++ b/Source/NSString.m
@@ -2564,7 +2564,15 @@ handle_printf_atsign (FILE *stream,
       unsigned	length = [d length];
       BOOL	result = (length <= maxLength) ? YES : NO;
 
-      if (length > maxLength) length = maxLength;
+      if (d == nil)
+        {
+	  [NSException raise: NSCharacterConversionException
+		      format: @"Can't convert to C string."];
+	}
+      if (length > maxLength)
+        {
+          length = maxLength;
+	}
       memcpy(buffer, [d bytes], length);
       buffer[length] = '\0';
       return result;
diff --git a/Source/NSURL.m b/Source/NSURL.m
index 8ee6d56cb..4b996b7d9 100644
--- a/Source/NSURL.m
+++ b/Source/NSURL.m
@@ -700,21 +700,24 @@ static unsigned	urlAlign;
       /*
        * Set up scheme specific parsing options.
        */
-      if (buf->scheme != 0)
+      if (buf->scheme == 0)
+        {
+	  DESTROY(self);	// Not a valid URL
+	  NS_VALRETURN(nil);
+	}
+
+      if (strcmp(buf->scheme, "file") == 0)
 	{
-	  if (strcmp(buf->scheme, "file") == 0)
-	    {
-	      usesFragments = NO;
-	      usesParameters = NO;
-	      usesQueries = NO;
-	      buf->isFile = YES;
-	    }
-	  else if (strcmp(buf->scheme, "mailto") == 0)
-	    {
-	      usesFragments = NO;
-	      usesParameters = NO;
-	      usesQueries = NO;
-	    }
+	  usesFragments = NO;
+	  usesParameters = NO;
+	  usesQueries = NO;
+	  buf->isFile = YES;
+	}
+      else if (strcmp(buf->scheme, "mailto") == 0)
+	{
+	  usesFragments = NO;
+	  usesParameters = NO;
+	  usesQueries = NO;
 	}
 
       if (canBeGeneric == YES)