diff --git a/glib/gtypes.h b/glib/gtypes.h
index 0e73b40b9..5b7a95ee7 100644
--- a/glib/gtypes.h
+++ b/glib/gtypes.h
@@ -58,19 +58,19 @@ typedef float   gfloat;
 typedef double  gdouble;
 
 /* Define min and max constants for the fixed size numerical types */
-#define G_MININT8	((gint8)  0x80)
+#define G_MININT8	((gint8) -0x80)
 #define G_MAXINT8	((gint8)  0x7f)
 #define G_MAXUINT8	((guint8) 0xff)
 
-#define G_MININT16	((gint16)  0x8000)
+#define G_MININT16	((gint16) -0x8000)
 #define G_MAXINT16	((gint16)  0x7fff)
 #define G_MAXUINT16	((guint16) 0xffff)
 
-#define G_MININT32	((gint32)  0x80000000)
+#define G_MININT32	((gint32) -0x80000000)
 #define G_MAXINT32	((gint32)  0x7fffffff)
 #define G_MAXUINT32	((guint32) 0xffffffff)
 
-#define G_MININT64	((gint64) G_GINT64_CONSTANT(0x8000000000000000))
+#define G_MININT64	((gint64) G_GINT64_CONSTANT(-0x8000000000000000))
 #define G_MAXINT64	G_GINT64_CONSTANT(0x7fffffffffffffff)
 #define G_MAXUINT64	G_GINT64_CONSTANT(0xffffffffffffffffU)