diff --git a/library/aes.c b/library/aes.c
index ec9313de3..36660306e 100644
--- a/library/aes.c
+++ b/library/aes.c
@@ -56,7 +56,7 @@
 
 /* Implementation that should never be optimized out by the compiler */
 static void mbedtls_zeroize( void *v, size_t n ) {
-    volatile unsigned char *p = v; while( n-- ) *p++ = 0;
+    volatile unsigned char *p = (unsigned char*)v; while( n-- ) *p++ = 0;
 }
 
 /*
diff --git a/library/arc4.c b/library/arc4.c
index ff0e993e7..05b33d3fd 100644
--- a/library/arc4.c
+++ b/library/arc4.c
@@ -49,7 +49,7 @@
 
 /* Implementation that should never be optimized out by the compiler */
 static void mbedtls_zeroize( void *v, size_t n ) {
-    volatile unsigned char *p = v; while( n-- ) *p++ = 0;
+    volatile unsigned char *p = (unsigned char*)v; while( n-- ) *p++ = 0;
 }
 
 void mbedtls_arc4_init( mbedtls_arc4_context *ctx )
diff --git a/library/asn1parse.c b/library/asn1parse.c
index b37523def..e59d2509f 100644
--- a/library/asn1parse.c
+++ b/library/asn1parse.c
@@ -45,7 +45,7 @@
 
 /* Implementation that should never be optimized out by the compiler */
 static void mbedtls_zeroize( void *v, size_t n ) {
-    volatile unsigned char *p = v; while( n-- ) *p++ = 0;
+    volatile unsigned char *p = (unsigned char*)v; while( n-- ) *p++ = 0;
 }
 
 /*
diff --git a/library/blowfish.c b/library/blowfish.c
index 89be4d122..9003f0dfe 100644
--- a/library/blowfish.c
+++ b/library/blowfish.c
@@ -41,7 +41,7 @@
 
 /* Implementation that should never be optimized out by the compiler */
 static void mbedtls_zeroize( void *v, size_t n ) {
-    volatile unsigned char *p = v; while( n-- ) *p++ = 0;
+    volatile unsigned char *p = (unsigned char*)v; while( n-- ) *p++ = 0;
 }
 
 /*
diff --git a/library/camellia.c b/library/camellia.c
index e015ca24b..d50513fd0 100644
--- a/library/camellia.c
+++ b/library/camellia.c
@@ -50,7 +50,7 @@
 
 /* Implementation that should never be optimized out by the compiler */
 static void mbedtls_zeroize( void *v, size_t n ) {
-    volatile unsigned char *p = v; while( n-- ) *p++ = 0;
+    volatile unsigned char *p = (unsigned char*)v; while( n-- ) *p++ = 0;
 }
 
 /*
diff --git a/library/ccm.c b/library/ccm.c
index 3463a0b32..13a8fd1a2 100644
--- a/library/ccm.c
+++ b/library/ccm.c
@@ -51,7 +51,7 @@
 
 /* Implementation that should never be optimized out by the compiler */
 static void mbedtls_zeroize( void *v, size_t n ) {
-    volatile unsigned char *p = v; while( n-- ) *p++ = 0;
+    volatile unsigned char *p = (unsigned char*)v; while( n-- ) *p++ = 0;
 }
 
 #define CCM_ENCRYPT 0
diff --git a/library/cipher.c b/library/cipher.c
index ccc068503..0dc51520f 100644
--- a/library/cipher.c
+++ b/library/cipher.c
@@ -51,7 +51,7 @@
 
 /* Implementation that should never be optimized out by the compiler */
 static void mbedtls_zeroize( void *v, size_t n ) {
-    volatile unsigned char *p = v; while( n-- ) *p++ = 0;
+    volatile unsigned char *p = (unsigned char*)v; while( n-- ) *p++ = 0;
 }
 
 static int supported_init = 0;
diff --git a/library/des.c b/library/des.c
index 61f214af3..09f95cfc3 100644
--- a/library/des.c
+++ b/library/des.c
@@ -50,7 +50,7 @@
 
 /* Implementation that should never be optimized out by the compiler */
 static void mbedtls_zeroize( void *v, size_t n ) {
-    volatile unsigned char *p = v; while( n-- ) *p++ = 0;
+    volatile unsigned char *p = (unsigned char*)v; while( n-- ) *p++ = 0;
 }
 
 /*
diff --git a/library/sha1.c b/library/sha1.c
index 8c77cbaa8..2ccf2a2f5 100644
--- a/library/sha1.c
+++ b/library/sha1.c
@@ -49,7 +49,7 @@
 
 /* Implementation that should never be optimized out by the compiler */
 static void mbedtls_zeroize( void *v, size_t n ) {
-    volatile unsigned char *p = v; while( n-- ) *p++ = 0;
+    volatile unsigned char *p = (unsigned char*)v; while( n-- ) *p++ = 0;
 }
 
 /*