diff --git a/library/md2.c b/library/md2.c
index 5ebf07232..e6e39c0ac 100644
--- a/library/md2.c
+++ b/library/md2.c
@@ -287,8 +287,8 @@ static const unsigned char md2_test_str[7][81] =
     { "message digest" },
     { "abcdefghijklmnopqrstuvwxyz" },
     { "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789" },
-    { "12345678901234567890123456789012345678901234567890123456789012"
-      "345678901234567890" }
+    { ("12345678901234567890123456789012345678901234567890123456789012"
+      "345678901234567890") }
 };
 
 static const size_t md2_test_strlen[7] =
diff --git a/library/md4.c b/library/md4.c
index ac9507454..7fadfca64 100644
--- a/library/md4.c
+++ b/library/md4.c
@@ -408,8 +408,8 @@ static const unsigned char md4_test_str[7][81] =
     { "message digest" },
     { "abcdefghijklmnopqrstuvwxyz" },
     { "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789" },
-    { "12345678901234567890123456789012345678901234567890123456789012"
-      "345678901234567890" }
+    { ("12345678901234567890123456789012345678901234567890123456789012"
+      "345678901234567890") }
 };
 
 static const size_t md4_test_strlen[7] =
diff --git a/library/md5.c b/library/md5.c
index 8cea902ae..147e94b4b 100644
--- a/library/md5.c
+++ b/library/md5.c
@@ -422,8 +422,8 @@ static const unsigned char md5_test_buf[7][81] =
     { "message digest" },
     { "abcdefghijklmnopqrstuvwxyz" },
     { "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789" },
-    { "12345678901234567890123456789012345678901234567890123456789012"
-      "345678901234567890" }
+    { ("12345678901234567890123456789012345678901234567890123456789012"
+      "345678901234567890") }
 };
 
 static const size_t md5_test_buflen[7] =
diff --git a/library/ripemd160.c b/library/ripemd160.c
index 830f61b3c..abb92b7a2 100644
--- a/library/ripemd160.c
+++ b/library/ripemd160.c
@@ -478,8 +478,8 @@ static const unsigned char ripemd160_test_str[TESTS][81] =
     { "abcdefghijklmnopqrstuvwxyz" },
     { "abcdbcdecdefdefgefghfghighijhijkijkljklmklmnlmnomnopnopq" },
     { "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789" },
-    { "12345678901234567890123456789012345678901234567890123456789012"
-      "345678901234567890" },
+    { ("12345678901234567890123456789012345678901234567890123456789012"
+      "345678901234567890") },
 };
 
 static const size_t ripemd160_test_strlen[TESTS] =
diff --git a/library/sha512.c b/library/sha512.c
index 80219d428..a3a28525c 100644
--- a/library/sha512.c
+++ b/library/sha512.c
@@ -516,8 +516,8 @@ void mbedtls_sha512( const unsigned char *input,
 static const unsigned char sha512_test_buf[3][113] =
 {
     { "abc" },
-    { "abcdefghbcdefghicdefghijdefghijkefghijklfghijklmghijklmn"
-      "hijklmnoijklmnopjklmnopqklmnopqrlmnopqrsmnopqrstnopqrstu" },
+    { ("abcdefghbcdefghicdefghijdefghijkefghijklfghijklmghijklmn"
+      "hijklmnoijklmnopjklmnopqklmnopqrlmnopqrsmnopqrstnopqrstu") },
     { "" }
 };