diff --git a/fsliolib/fslio.c b/fsliolib/fslio.c
index 44053fcf..75d2bfde 100644
--- a/fsliolib/fslio.c
+++ b/fsliolib/fslio.c
@@ -1756,7 +1756,7 @@ int FslGetIntensityScaling(FSLIO *fslio, float *slope, float *intercept)
 
 mat33 mat44_to_mat33(mat44 x)
 {
-  mat33 y;
+  mat33 y = { { { 0.0f } } };
   int i,j;
   for (i=0; i<3; i++) {
     for (j=0; j<3; j++) {
diff --git a/nifti2/nifti2_io.c b/nifti2/nifti2_io.c
index 70c136e8..3fd44dd7 100644
--- a/nifti2/nifti2_io.c
+++ b/nifti2/nifti2_io.c
@@ -2451,7 +2451,7 @@ float nifti_mat33_colnorm( mat33 A )  /* max column norm of 3x3 matrix */
 nifti_dmat33 nifti_dmat33_mul( nifti_dmat33 A , nifti_dmat33 B )
 /* multiply 2 3x3 matrices */
 {
-   nifti_dmat33 C ; int i,j ;
+   nifti_dmat33 C = { { { 0.0 } } } ; int i,j ;
    for( i=0 ; i < 3 ; i++ )
     for( j=0 ; j < 3 ; j++ )
       C.m[i][j] =  A.m[i][0] * B.m[0][j]
@@ -2465,7 +2465,7 @@ nifti_dmat33 nifti_dmat33_mul( nifti_dmat33 A , nifti_dmat33 B )
 *//*--------------------------------------------------------------------*/
 mat33 nifti_mat33_mul( mat33 A , mat33 B )  /* multiply 2 3x3 matrices */
 {
-   mat33 C ; int i,j ;
+   mat33 C = { { { 0.0f } } } ; int i,j ;
    for( i=0 ; i < 3 ; i++ )
     for( j=0 ; j < 3 ; j++ )
       C.m[i][j] =  A.m[i][0] * B.m[0][j]
@@ -2479,7 +2479,7 @@ mat33 nifti_mat33_mul( mat33 A , mat33 B )  /* multiply 2 3x3 matrices */
 *//*--------------------------------------------------------------------*/
 nifti_dmat44 nifti_dmat44_mul( nifti_dmat44 A , nifti_dmat44 B )
 {
-   nifti_dmat44 C ; int i,j,k ;
+   nifti_dmat44 C = { { { 0.0 } } } ; int i,j,k ;
    for( i=0 ; i < 4 ; i++ )
       for( j=0 ; j < 4 ; j++ ) {
          C.m[i][j] = 0.0;
@@ -2494,7 +2494,7 @@ nifti_dmat44 nifti_dmat44_mul( nifti_dmat44 A , nifti_dmat44 B )
 *//*--------------------------------------------------------------------*/
 mat44 nifti_mat44_mul( mat44 A , mat44 B )
 {
-   mat44 C ; int i,j,k ;
+   mat44 C = { { { 0.0f } } } ; int i,j,k ;
    for( i=0 ; i < 4 ; i++ )
       for( j=0 ; j < 4 ; j++ ) {
          C.m[i][j] = 0.0;
diff --git a/niftilib/nifti1_io.c b/niftilib/nifti1_io.c
index c9142554..bbbb236c 100644
--- a/niftilib/nifti1_io.c
+++ b/niftilib/nifti1_io.c
@@ -1887,7 +1887,7 @@ float nifti_mat33_colnorm( mat33 A )  /* max column norm of 3x3 matrix */
 *//*--------------------------------------------------------------------*/
 mat33 nifti_mat33_mul( mat33 A , mat33 B )  /* multiply 2 3x3 matrices */
 {
-   mat33 C ; int i,j ;
+   mat33 C = { { { 0.0f } } } ; int i,j ;
    for( i=0 ; i < 3 ; i++ )
     for( j=0 ; j < 3 ; j++ )
       C.m[i][j] =  A.m[i][0] * B.m[0][j]
diff --git a/niftilib/nifti_tester001.c b/niftilib/nifti_tester001.c
index 126e6bd6..b44ba9f2 100644
--- a/niftilib/nifti_tester001.c
+++ b/niftilib/nifti_tester001.c
@@ -636,7 +636,7 @@ int main (int argc, const char *argv[])
   nifti_datatype_sizes_test(DT_COMPLEX256,32,16);
 
   {
-  mat44 R;
+  mat44 R = { { { 0.0f } } };
   unsigned i,j;
   for(i = 0; i < 4; i++)
     for(j = 0; j < 4; j++)