diff --git a/tests/scripts/all.sh b/tests/scripts/all.sh
index 515b0b7d86..3e52e6e84b 100755
--- a/tests/scripts/all.sh
+++ b/tests/scripts/all.sh
@@ -794,7 +794,7 @@ component_test_full_cmake_gcc_asan () {
 component_test_zlib_make() {
     msg "build: zlib enabled, make"
     scripts/config.pl set MBEDTLS_ZLIB_SUPPORT
-    make ZLIB=1 CFLAGS='-Werror -O1'
+    make ZLIB=1 CFLAGS='-Werror -O2'
 
     msg "test: main suites (zlib, make)"
     make test
@@ -817,7 +817,7 @@ EOF
 component_test_zlib_cmake() {
     msg "build: zlib enabled, cmake"
     scripts/config.pl set MBEDTLS_ZLIB_SUPPORT
-    cmake -D ENABLE_ZLIB_SUPPORT=On -D CMAKE_BUILD_TYPE:String=Check .
+    cmake -D ENABLE_ZLIB_SUPPORT=On -D CMAKE_BUILD_TYPE:String=Release .
     make
 
     msg "test: main suites (zlib, cmake)"
@@ -1055,7 +1055,7 @@ component_test_small_mbedtls_ssl_dtls_max_buffering () {
 component_test_full_cmake_clang () {
     msg "build: cmake, full config, clang" # ~ 50s
     scripts/config.pl full
-    CC=clang cmake -D CMAKE_BUILD_TYPE:String=Check -D ENABLE_TESTING=On .
+    CC=clang cmake -D CMAKE_BUILD_TYPE:String=Release -D ENABLE_TESTING=On .
     make
 
     msg "test: main suites (full config)" # ~ 5s
@@ -1266,7 +1266,7 @@ component_test_memory_buffer_allocator_backtrace () {
     scripts/config.pl set MBEDTLS_PLATFORM_MEMORY
     scripts/config.pl set MBEDTLS_MEMORY_BACKTRACE
     scripts/config.pl set MBEDTLS_MEMORY_DEBUG
-    CC=gcc cmake .
+    CC=gcc cmake -DCMAKE_BUILD_TYPE:String=Release .
     make
 
     msg "test: MBEDTLS_MEMORY_BUFFER_ALLOC_C and MBEDTLS_MEMORY_BACKTRACE"
@@ -1277,7 +1277,7 @@ component_test_memory_buffer_allocator () {
     msg "build: default config with memory buffer allocator"
     scripts/config.pl set MBEDTLS_MEMORY_BUFFER_ALLOC_C
     scripts/config.pl set MBEDTLS_PLATFORM_MEMORY
-    CC=gcc cmake .
+    CC=gcc cmake -DCMAKE_BUILD_TYPE:String=Release .
     make
 
     msg "test: MBEDTLS_MEMORY_BUFFER_ALLOC_C"
@@ -1330,7 +1330,7 @@ component_test_null_entropy () {
 component_test_no_date_time () {
     msg "build: default config without MBEDTLS_HAVE_TIME_DATE"
     scripts/config.pl unset MBEDTLS_HAVE_TIME_DATE
-    CC=gcc cmake
+    CC=gcc cmake -D CMAKE_BUILD_TYPE:String=Check .
     make
 
     msg "test: !MBEDTLS_HAVE_TIME_DATE - main suites"
@@ -1442,7 +1442,8 @@ component_build_mbedtls_config_file () {
 }
 
 component_test_m32_o0 () {
-    # Build once with -O0, to compile out the i386 specific inline assembly
+    # Build without optimization, so as to use portable C code (in a 32-bit
+    # build) and not the i386-specific inline assembly.
     msg "build: i386, make, gcc -O0 (ASan build)" # ~ 30s
     scripts/config.pl full
     make CC=gcc CFLAGS="$ASAN_CFLAGS -m32 -O0" LDFLAGS="-m32 $ASAN_CFLAGS"
@@ -1457,19 +1458,20 @@ support_test_m32_o0 () {
     esac
 }
 
-component_test_m32_o1 () {
-    # Build again with -O1, to compile in the i386 specific inline assembly
-    msg "build: i386, make, gcc -O1 (ASan build)" # ~ 30s
+component_test_m32_o2 () {
+    # Build with optimization, to use the i386 specific inline assembly
+    # and go faster for tests.
+    msg "build: i386, make, gcc -O2 (ASan build)" # ~ 30s
     scripts/config.pl full
-    make CC=gcc CFLAGS="$ASAN_CFLAGS -m32 -O1" LDFLAGS="-m32 $ASAN_CFLAGS"
+    make CC=gcc CFLAGS="$ASAN_CFLAGS -m32 -O2" LDFLAGS="-m32 $ASAN_CFLAGS"
 
-    msg "test: i386, make, gcc -O1 (ASan build)"
+    msg "test: i386, make, gcc -O2 (ASan build)"
     make test
 
-    msg "test ssl-opt.sh, i386, make, gcc-O1"
+    msg "test ssl-opt.sh, i386, make, gcc-O2"
     if_build_succeeded tests/ssl-opt.sh
 }
-support_test_m32_o1 () {
+support_test_m32_o2 () {
     support_test_m32_o0 "$@"
 }
 
@@ -1720,7 +1722,7 @@ component_test_cmake_out_of_source () {
     MBEDTLS_ROOT_DIR="$PWD"
     mkdir "$OUT_OF_SOURCE_DIR"
     cd "$OUT_OF_SOURCE_DIR"
-    cmake "$MBEDTLS_ROOT_DIR"
+    cmake -D CMAKE_BUILD_TYPE:String=Check "$MBEDTLS_ROOT_DIR"
     make
 
     msg "test: cmake 'out-of-source' build"