diff --git a/tests/scripts/all.sh b/tests/scripts/all.sh
index 91b326e..9cb3ec1 100755
--- a/tests/scripts/all.sh
+++ b/tests/scripts/all.sh
@@ -1109,8 +1109,8 @@
     scripts/config.pl unset MBEDTLS_FS_IO
     # Note, _DEFAULT_SOURCE needs to be defined for platforms using glibc version >2.19,
     # to re-enable platform integration features otherwise disabled in C99 builds
-    make CC=gcc PTHREAD=1 CFLAGS='-Werror -Wall -Wextra -std=c99 -pedantic -O0 -D_DEFAULT_SOURCE' lib programs
-    make CC=gcc PTHREAD=1 CFLAGS='-Werror -Wall -Wextra -O0' test
+    make CC=gcc PTHREAD=1 CFLAGS='-Werror -Wall -Wextra -std=c99 -pedantic -Os -D_DEFAULT_SOURCE' lib programs
+    make CC=gcc PTHREAD=1 CFLAGS='-Werror -Wall -Wextra -Os' test
 }
 
 component_build_no_std_function () {
@@ -1119,21 +1119,21 @@
     scripts/config.pl full
     scripts/config.pl set MBEDTLS_PLATFORM_NO_STD_FUNCTIONS
     scripts/config.pl unset MBEDTLS_ENTROPY_NV_SEED
-    make CC=gcc PTHREAD=1 CFLAGS='-Werror -Wall -Wextra -O0'
+    make CC=gcc PTHREAD=1 CFLAGS='-Werror -Wall -Wextra -Os'
 }
 
 component_build_no_ssl_srv () {
     msg "build: full config except ssl_srv.c, make, gcc" # ~ 30s
     scripts/config.pl full
     scripts/config.pl unset MBEDTLS_SSL_SRV_C
-    make CC=gcc PTHREAD=1 CFLAGS='-Werror -Wall -Wextra -O0'
+    make CC=gcc PTHREAD=1 CFLAGS='-Werror -Wall -Wextra -O1'
 }
 
 component_build_no_ssl_cli () {
     msg "build: full config except ssl_cli.c, make, gcc" # ~ 30s
     scripts/config.pl full
     scripts/config.pl unset MBEDTLS_SSL_CLI_C
-    make CC=gcc PTHREAD=1 CFLAGS='-Werror -Wall -Wextra -O0'
+    make CC=gcc PTHREAD=1 CFLAGS='-Werror -Wall -Wextra -O1'
 }
 
 component_build_no_sockets () {
@@ -1143,7 +1143,7 @@
     scripts/config.pl full
     scripts/config.pl unset MBEDTLS_NET_C # getaddrinfo() undeclared, etc.
     scripts/config.pl set MBEDTLS_NO_PLATFORM_ENTROPY # uses syscall() on GNU/Linux
-    make CC=gcc PTHREAD=1 CFLAGS='-Werror -Wall -Wextra -O0 -std=c99 -pedantic' lib
+    make CC=gcc PTHREAD=1 CFLAGS='-Werror -Wall -Wextra -O1 -std=c99 -pedantic' lib
 }
 
 component_test_memory_buffer_allocator_backtrace () {