diff --git a/ports/esp32/boards/sdkconfig.base b/ports/esp32/boards/sdkconfig.base
index 9348f40632..2c77c20907 100644
--- a/ports/esp32/boards/sdkconfig.base
+++ b/ports/esp32/boards/sdkconfig.base
@@ -28,6 +28,10 @@ CONFIG_LWIP_PPP_SUPPORT=y
 CONFIG_LWIP_PPP_PAP_SUPPORT=y
 CONFIG_LWIP_PPP_CHAP_SUPPORT=y
 
+# SSL
+# Use 4kiB output buffer instead of default 16kiB (because IDF heap is fragmented in 4.0)
+CONFIG_MBEDTLS_ASYMMETRIC_CONTENT_LEN=y
+
 # v3.3-only (renamed in 4.0)
 CONFIG_LOG_BOOTLOADER_LEVEL_WARN=y
 CONFIG_TASK_WDT_CHECK_IDLE_TASK_CPU0=n