diff --git a/simgear/debug/logstream.cxx b/simgear/debug/logstream.cxx
index 01079e97..a7d69ff7 100644
--- a/simgear/debug/logstream.cxx
+++ b/simgear/debug/logstream.cxx
@@ -531,7 +531,7 @@ logstream::log( sgDebugClass c, sgDebugPriority p,
 }
 
 
-void logstream::hexdump(sgDebugClass c, sgDebugPriority p, const char* fileName, int line, const void *mem, unsigned int len, int columns)
+void logstream::hexdump(sgDebugClass c, sgDebugPriority p, const char* fileName, int line, const void *mem, unsigned int len, unsigned int columns)
 {
     unsigned int i, j;
     char temp[3000], temp1[3000];
diff --git a/simgear/debug/logstream.hxx b/simgear/debug/logstream.hxx
index c00657e0..32e19e95 100644
--- a/simgear/debug/logstream.hxx
+++ b/simgear/debug/logstream.hxx
@@ -120,7 +120,7 @@ public:
     /**
     * output formatted hex dump of memory block
     */
-    void hexdump(sgDebugClass c, sgDebugPriority p, const char* fileName, int line, const void *mem, unsigned int len, int columns = 16);
+    void hexdump(sgDebugClass c, sgDebugPriority p, const char* fileName, int line, const void *mem, unsigned int len, unsigned int columns = 16);
 
 
     /**