diff --git a/wolfssl/internal.h b/wolfssl/internal.h
index 943e07d26f..e914a78132 100644
--- a/wolfssl/internal.h
+++ b/wolfssl/internal.h
@@ -3447,7 +3447,7 @@ typedef struct SignatureAlgorithms {
     #pragma warning(disable: 4200)
     #endif
     /* sig/algo to offer */
-    byte        hashSigAlgo[WC_FLEXIBLE_ARRAY_MEMBER];
+    byte        hashSigAlgo[WC_FLEXIBLE_ARRAY_SIZE];
 } SignatureAlgorithms;
 
 WOLFSSL_LOCAL SignatureAlgorithms* TLSX_SignatureAlgorithms_New(
@@ -3630,7 +3630,7 @@ typedef struct ExternalTicket {
     byte key_name[WOLFSSL_TICKET_NAME_SZ];     /* key context name - 16 */
     byte iv[WOLFSSL_TICKET_IV_SZ];             /* this ticket's iv - 16 */
     byte enc_len[OPAQUE16_LEN];                /* encrypted length - 2 */
-    byte enc_ticket[WC_FLEXIBLE_ARRAY_MEMBER]; /* encrypted ticket - var length
+    byte enc_ticket[WC_FLEXIBLE_ARRAY_SIZE]; /* encrypted ticket - var length
                                                 *   + total mac - 32 */
 } ExternalTicket;
 
@@ -3715,7 +3715,7 @@ typedef struct Cookie {
     #ifdef _MSC_VER
     #pragma warning(disable: 4200)
     #endif
-    byte   data[WC_FLEXIBLE_ARRAY_MEMBER];
+    byte   data[WC_FLEXIBLE_ARRAY_SIZE];
 } Cookie;
 
 WOLFSSL_LOCAL int TLSX_Cookie_Use(const WOLFSSL* ssl, const byte* data,
@@ -5771,7 +5771,7 @@ typedef struct DtlsFragBucket {
 #ifdef _MSC_VER
 #pragma warning(disable: 4200)
 #endif
-    byte buf[WC_FLEXIBLE_ARRAY_MEMBER];
+    byte buf[WC_FLEXIBLE_ARRAY_SIZE];
 } DtlsFragBucket;
 
 typedef struct DtlsMsg {
diff --git a/wolfssl/wolfcrypt/types.h b/wolfssl/wolfcrypt/types.h
index 3f3a7839fa..fc37b4a569 100644
--- a/wolfssl/wolfcrypt/types.h
+++ b/wolfssl/wolfcrypt/types.h
@@ -221,13 +221,27 @@ typedef const char wcchar[];
     #define WOLF_ENUM_DUMMY_LAST_ELEMENT(prefix) /* null expansion */
 #endif
 
-#if defined(WOLF_C89)
-    /* C99 flexible array member, or the C89 "struct hack" fallback.
+#if defined(WC_FLEXIBLE_ARRAY_SIZE)
+    /* keep override value. */
+#elif defined(__cplusplus)
+    /* No C++ standard has FAMs; [] and [0] are vendor extensions.
+     * Use the struct hack. */
+    #define WC_FLEXIBLE_ARRAY_SIZE 1
+#elif defined(__STDC_VERSION__) && (__STDC_VERSION__ >= 199901L)
+    /* Standard C99+ flexible array member -- valid even under
+     * __STRICT_ANSI__ / -pedantic. */
+    #define WC_FLEXIBLE_ARRAY_SIZE
+#elif defined(__STRICT_ANSI__) || defined(WOLF_C89)
+    /* C89 "struct hack" fallback.
      * See http://c-faq.com/struct/structhack.html */
-    #define WC_FLEXIBLE_ARRAY_MEMBER 1
+    #define WC_FLEXIBLE_ARRAY_SIZE 1
+#elif defined(__GNUC__) || defined(__clang__) || \
+      (defined(_MSC_VER) && !defined(__cplusplus))
+    /* gnu89 etc.: [] accepted as an extension without -pedantic;
+     * MSVC C mode accepts it too (C4200, off by default at /W3). */
+    #define WC_FLEXIBLE_ARRAY_SIZE
 #else
-    /* empty: C99 flexible array member */
-    #define WC_FLEXIBLE_ARRAY_MEMBER
+    #define WC_FLEXIBLE_ARRAY_SIZE 1
 #endif
 
 /* try to set SIZEOF_LONG or SIZEOF_LONG_LONG if user didn't */