diff --git a/configs/config-ccm-psk-dtls1_2.h b/configs/config-ccm-psk-dtls1_2.h
index 9150e05..0be4f05 100644
--- a/configs/config-ccm-psk-dtls1_2.h
+++ b/configs/config-ccm-psk-dtls1_2.h
@@ -99,6 +99,11 @@
 //#define MBEDTLS_USE_PSA_CRYPTO
 //#define MBEDTLS_PSA_CRYPTO_C
 
+/* Error messages and TLS debugging traces
+ * (huge code size increase, needed for tests/ssl-opt.sh) */
+//#define MBEDTLS_DEBUG_C
+//#define MBEDTLS_ERROR_C
+
 #include "mbedtls/check_config.h"
 
 #endif /* MBEDTLS_CONFIG_H */
diff --git a/configs/config-ccm-psk-tls1_2.h b/configs/config-ccm-psk-tls1_2.h
index 0e8f570..ca1e6c9 100644
--- a/configs/config-ccm-psk-tls1_2.h
+++ b/configs/config-ccm-psk-tls1_2.h
@@ -90,6 +90,11 @@
 //#define MBEDTLS_USE_PSA_CRYPTO
 //#define MBEDTLS_PSA_CRYPTO_C
 
+/* Error messages and TLS debugging traces
+ * (huge code size increase, needed for tests/ssl-opt.sh) */
+//#define MBEDTLS_DEBUG_C
+//#define MBEDTLS_ERROR_C
+
 #include "mbedtls/check_config.h"
 
 #endif /* MBEDTLS_CONFIG_H */
diff --git a/configs/config-mini-tls1_1.h b/configs/config-mini-tls1_1.h
index 9092829..78e31d5 100644
--- a/configs/config-mini-tls1_1.h
+++ b/configs/config-mini-tls1_1.h
@@ -82,4 +82,9 @@
 #endif
 #include "mbedtls/check_config.h"
 
+/* Error messages and TLS debugging traces
+ * (huge code size increase, needed for tests/ssl-opt.sh) */
+//#define MBEDTLS_DEBUG_C
+//#define MBEDTLS_ERROR_C
+
 #endif /* MBEDTLS_CONFIG_H */
diff --git a/configs/config-suite-b.h b/configs/config-suite-b.h
index 05f14c8..3923ec0 100644
--- a/configs/config-suite-b.h
+++ b/configs/config-suite-b.h
@@ -119,6 +119,11 @@
 #define MBEDTLS_PK_WRITE_C
 #endif
 
+/* Error messages and TLS debugging traces
+ * (huge code size increase, needed for tests/ssl-opt.sh) */
+//#define MBEDTLS_DEBUG_C
+//#define MBEDTLS_ERROR_C
+
 #include "mbedtls/check_config.h"
 
 #endif /* MBEDTLS_CONFIG_H */