diff --git a/library/pk_wrap.c b/library/pk_wrap.c
index 6f22b09..eb87d3c 100644
--- a/library/pk_wrap.c
+++ b/library/pk_wrap.c
@@ -57,7 +57,7 @@
 #if defined(POLARSSL_RSA_C)
 static size_t rsa_get_size( const void *ctx )
 {
-    return( 8 * ((rsa_context *) ctx)->len );
+    return( 8 * ((const rsa_context *) ctx)->len );
 }
 
 static int rsa_verify_wrap( void *ctx, md_type_t md_alg,
@@ -346,7 +346,7 @@
 
 static size_t rsa_alt_get_size( const void *ctx )
 {
-    rsa_alt_context *rsa_alt = (rsa_alt_context *) ctx;
+    const rsa_alt_context *rsa_alt = (const rsa_alt_context *) ctx;
 
     return( rsa_alt->key_len_func( rsa_alt->key ) );
 }
diff --git a/programs/pkey/ecdsa.c b/programs/pkey/ecdsa.c
index 948066a..3cba7e8 100644
--- a/programs/pkey/ecdsa.c
+++ b/programs/pkey/ecdsa.c
@@ -60,7 +60,7 @@
 #else
 
 #if defined(VERBOSE)
-static void dump_buf( char *title, unsigned char *buf, size_t len )
+static void dump_buf( const char *title, unsigned char *buf, size_t len )
 {
     size_t i;
 
@@ -71,7 +71,7 @@
     printf( "\n" );
 }
 
-static void dump_pubkey( char *title, ecdsa_context *key )
+static void dump_pubkey( const char *title, ecdsa_context *key )
 {
     unsigned char buf[300];
     size_t len;
diff --git a/programs/util/pem2der.c b/programs/util/pem2der.c
index 9364356..f372684 100644
--- a/programs/util/pem2der.c
+++ b/programs/util/pem2der.c
@@ -50,8 +50,8 @@
  */
 struct options
 {
-    char *filename;             /* filename of the input file             */
-    char *output_file;          /* where to store the output              */
+    const char *filename;       /* filename of the input file             */
+    const char *output_file;    /* where to store the output              */
 } opt;
 
 int convert_pem_to_der( const unsigned char *input, size_t ilen,
@@ -61,11 +61,11 @@
     const unsigned char *s1, *s2, *end = input + ilen;
     size_t len = 0;
 
-    s1 = (unsigned char *) strstr( (char *) input, "-----BEGIN" );
+    s1 = (unsigned char *) strstr( (const char *) input, "-----BEGIN" );
     if( s1 == NULL )
         return( -1 );
 
-    s2 = (unsigned char *) strstr( (char *) input, "-----END" );
+    s2 = (unsigned char *) strstr( (const char *) input, "-----END" );
     if( s2 == NULL )
         return( -1 );
 
diff --git a/programs/x509/cert_req.c b/programs/x509/cert_req.c
index dc45f94..2388dc9 100644
--- a/programs/x509/cert_req.c
+++ b/programs/x509/cert_req.c
@@ -62,15 +62,15 @@
  */
 struct options
 {
-    char *filename;             /* filename of the key file             */
+    const char *filename;       /* filename of the key file             */
     int debug_level;            /* level of debugging                   */
-    char *output_file;          /* where to store the constructed key file  */
-    char *subject_name;         /* subject name for certificate request */
+    const char *output_file;    /* where to store the constructed key file  */
+    const char *subject_name;   /* subject name for certificate request */
     unsigned char key_usage;    /* key usage flags                      */
     unsigned char ns_cert_type; /* NS cert type                         */
 } opt;
 
-int write_certificate_request( x509write_csr *req, char *output_file,
+int write_certificate_request( x509write_csr *req, const char *output_file,
                                int (*f_rng)(void *, unsigned char *, size_t),
                                void *p_rng )
 {
diff --git a/programs/x509/cert_write.c b/programs/x509/cert_write.c
index f72f623..beac089 100644
--- a/programs/x509/cert_write.c
+++ b/programs/x509/cert_write.c
@@ -75,18 +75,18 @@
  */
 struct options
 {
-    char *issuer_crt;           /* filename of the issuer certificate   */
-    char *request_file;         /* filename of the certificate request  */
-    char *subject_key;          /* filename of the subject key file     */
-    char *issuer_key;           /* filename of the issuer key file      */
-    char *subject_pwd;          /* password for the subject key file    */
-    char *issuer_pwd;           /* password for the issuer key file     */
-    char *output_file;          /* where to store the constructed key file  */
-    char *subject_name;         /* subject name for certificate         */
-    char *issuer_name;          /* issuer name for certificate          */
-    char *not_before;           /* validity period not before           */
-    char *not_after;            /* validity period not after            */
-    char *serial;               /* serial number string                 */
+    const char *issuer_crt;     /* filename of the issuer certificate   */
+    const char *request_file;   /* filename of the certificate request  */
+    const char *subject_key;    /* filename of the subject key file     */
+    const char *issuer_key;     /* filename of the issuer key file      */
+    const char *subject_pwd;    /* password for the subject key file    */
+    const char *issuer_pwd;     /* password for the issuer key file     */
+    const char *output_file;    /* where to store the constructed key file  */
+    const char *subject_name;   /* subject name for certificate         */
+    const char *issuer_name;    /* issuer name for certificate          */
+    const char *not_before;     /* validity period not before           */
+    const char *not_after;      /* validity period not after            */
+    const char *serial;         /* serial number string                 */
     int selfsign;               /* selfsign the certificate             */
     int is_ca;                  /* is a CA certificate                  */
     int max_pathlen;            /* maximum CA path length               */
@@ -94,7 +94,7 @@
     unsigned char ns_cert_type; /* NS cert type                         */
 } opt;
 
-int write_certificate( x509write_cert *crt, char *output_file,
+int write_certificate( x509write_cert *crt, const char *output_file,
                        int (*f_rng)(void *, unsigned char *, size_t),
                        void *p_rng )
 {
diff --git a/tests/suites/main_test.function b/tests/suites/main_test.function
index c64d9be..67fb394 100644
--- a/tests/suites/main_test.function
+++ b/tests/suites/main_test.function
@@ -6,7 +6,7 @@
 SUITE_PRE_DEP
 #define TEST_SUITE_ACTIVE
 
-static int test_assert( int correct, char *test )
+static int test_assert( int correct, const char *test )
 {
     if( correct )
         return( 0 );