diff --git a/examples/platforms/cc1352/crypto/cc1352-mbedtls-config.h b/examples/platforms/cc1352/crypto/cc1352-mbedtls-config.h
index d7509e5bd..c45f603af 100644
--- a/examples/platforms/cc1352/crypto/cc1352-mbedtls-config.h
+++ b/examples/platforms/cc1352/crypto/cc1352-mbedtls-config.h
@@ -31,4 +31,7 @@
 
 #define MBEDTLS_AES_ALT
 
+/* TODO: remove once AES alt driver supports 256-bit keys */
+#define MBEDTLS_CTR_DRBG_USE_128_BIT_KEY
+
 #endif // CC1352_MBEDTLS_CONFIG_H
diff --git a/examples/platforms/cc2650/crypto/cc2650-mbedtls-config.h b/examples/platforms/cc2650/crypto/cc2650-mbedtls-config.h
index 72a201af9..db4605814 100644
--- a/examples/platforms/cc2650/crypto/cc2650-mbedtls-config.h
+++ b/examples/platforms/cc2650/crypto/cc2650-mbedtls-config.h
@@ -32,4 +32,6 @@
 #define MBEDTLS_AES_ALT
 #define MBEDTLS_SHA256_ALT
 
+#define MBEDTLS_CTR_DRBG_USE_128_BIT_KEY
+
 #endif // CC2650_MBEDTLS_CONFIG_H
diff --git a/examples/platforms/cc2652/crypto/cc2652-mbedtls-config.h b/examples/platforms/cc2652/crypto/cc2652-mbedtls-config.h
index 399d9e3c2..3baa39455 100644
--- a/examples/platforms/cc2652/crypto/cc2652-mbedtls-config.h
+++ b/examples/platforms/cc2652/crypto/cc2652-mbedtls-config.h
@@ -31,4 +31,7 @@
 
 #define MBEDTLS_AES_ALT
 
+/* TODO: remove once AES alt driver supports 256-bit keys */
+#define MBEDTLS_CTR_DRBG_USE_128_BIT_KEY
+
 #endif // CC2652_MBEDTLS_CONFIG_H