diff --git a/src/g2_addfield.c b/src/g2_addfield.c
index ed90ed9e..76aba15e 100644
--- a/src/g2_addfield.c
+++ b/src/g2_addfield.c
@@ -108,7 +108,8 @@ g2_addfield(unsigned char *cgrib, g2int ipdsnum, g2int *ipdstmpl,
     g2int ilen, isecnum, i, nbits, temp, left;
     g2int ibmprev, j, lcpack, ioctet, newlen, ndpts;
     g2int lensec4, lensec5, lensec6, lensec7;
-    g2int issec3 = 0, isprevbmap = 0, lpos3 = 0, JJ, KK, MM;
+    g2int issec3 = 0, isprevbmap = 0, lpos3 = 0, JJ, KK;
+    g2intu MM;
     g2int *coordieee;
     float *pfld;
     gtemplate *mappds, *mapdrs;
diff --git a/src/grib2_int.h b/src/grib2_int.h
index 3e214109..82763bc1 100644
--- a/src/grib2_int.h
+++ b/src/grib2_int.h
@@ -336,7 +336,7 @@ void misspack(float *fld, g2int ndpts, g2int idrsnum, g2int *idrstmpl,
 void cmplxpack(float *fld, g2int ndpts, g2int idrsnum, g2int *idrstmpl,
                unsigned char *cpack, g2int *lcpack);
 g2int getpoly(unsigned char *csec3, g2int *jj, g2int *kk, g2int *mm);
-void specpack(float *fld, g2int ndpts, g2int JJ, g2int KK, g2int MM,
+void specpack(float *fld, g2int ndpts, g2int JJ, g2int KK, g2intu MM,
               g2int *idrstmpl, unsigned char *cpack, g2int *lcpack);
 g2int specunpack(unsigned char *cpack, g2int *idrstmpl, g2int ndpts, g2int JJ,
                  g2int KK, g2int MM, float *fld);
diff --git a/src/specpack.c b/src/specpack.c
index e2772d08..98ef0e1b 100644
--- a/src/specpack.c
+++ b/src/specpack.c
@@ -30,7 +30,7 @@
  * @author Stephen Gilbert @date 2002-12-19
  */
 void
-specpack(float *fld, g2int ndpts, g2int JJ, g2int KK, g2int MM,
+specpack(float *fld, g2int ndpts, g2int JJ, g2int KK, g2intu MM,
          g2int *idrstmpl, unsigned char *cpack, g2int *lcpack)
 {
 
diff --git a/tests/tst_spec.c b/tests/tst_spec.c
index c3c3cb86..82871bc8 100644
--- a/tests/tst_spec.c
+++ b/tests/tst_spec.c
@@ -24,7 +24,8 @@ main()
         unsigned char cpack[PACKED_LEN];
         g2int lcpack;
         g2int idrstmpl[10] = {0, 1, 1, 16, 0, 0, 0, 0, 2, 1};
-        g2int JJ = 1, KK = 1, MM = 1;
+        g2int JJ = 1, KK = 1;
+        g2intu MM = 1;
         int i;
 
         printf("Packing the data...");