diff --git a/CMakeLists.txt b/CMakeLists.txt
index 1334dececd..0c445b27b4 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -120,17 +120,11 @@ if(CMAKE_C_FLAGS_RELEASE MATCHES "-O3")
   string(REPLACE "-O3" "-O2" CMAKE_C_FLAGS_RELEASE "${CMAKE_C_FLAGS_RELEASE}")
 endif()
 
-if(CMAKE_C_COMPILER_ID MATCHES "GNU")
-  check_c_compiler_flag(-Og HAS_OG_FLAG)
-else()
-  set(HAS_OG_FLAG 0)
-endif()
-
-#
 # Build-type: RelWithDebInfo
-#
-if(HAS_OG_FLAG)
-  set(CMAKE_C_FLAGS_RELWITHDEBINFO "${CMAKE_C_FLAGS_RELWITHDEBINFO} -Og -g")
+
+# /Og means something different in MSVC
+if(CMAKE_C_COMPILER_ID MATCHES "GNU" OR CMAKE_C_COMPILER_ID MATCHES "Clang")
+   set(CMAKE_C_FLAGS_RELWITHDEBINFO "${CMAKE_C_FLAGS_RELWITHDEBINFO} -Og -g")
 endif()
 # We _want_ assertions in RelWithDebInfo build-type.
 if(CMAKE_C_FLAGS_RELWITHDEBINFO MATCHES DNDEBUG)
diff --git a/src/nvim/CMakeLists.txt b/src/nvim/CMakeLists.txt
index 504dde5a9c..10f44c428c 100755
--- a/src/nvim/CMakeLists.txt
+++ b/src/nvim/CMakeLists.txt
@@ -87,14 +87,14 @@ if(MSVC)
   target_sources(main_lib INTERFACE ${CMAKE_CURRENT_LIST_DIR}/os/nvim.manifest)
 else()
   target_compile_options(main_lib INTERFACE -Wall -Wextra -pedantic -Wno-unused-parameter
-    -Wstrict-prototypes -std=gnu99 -Wshadow -Wconversion
+    -Wstrict-prototypes -std=gnu99 -Wshadow -Wconversion -Wvla
     -Wdouble-promotion
     -Wmissing-noreturn
     -Wmissing-format-attribute
     -Wmissing-prototypes)
 
   if(CMAKE_C_COMPILER_ID STREQUAL "GNU")
-    target_compile_options(main_lib INTERFACE
+    target_compile_options(main_lib INTERFACE -fno-common
       $<$<CONFIG:Release>:-Wno-unused-result>
       $<$<CONFIG:RelWithDebInfo>:-Wno-unused-result>
       $<$<CONFIG:MinSizeRel>:-Wno-unused-result>)
@@ -144,17 +144,6 @@ if(WIN32)
   target_compile_definitions(main_lib INTERFACE _WIN32_WINNT=0x0602 MSWIN)
 endif()
 
-# OpenBSD's GCC (4.2.1) doesn't have -Wvla
-check_c_compiler_flag(-Wvla HAS_WVLA_FLAG)
-if(HAS_WVLA_FLAG)
-  target_compile_options(main_lib INTERFACE -Wvla)
-endif()
-
-check_c_compiler_flag(-fno-common HAVE_FNO_COMMON)
-if (HAVE_FNO_COMMON)
-  target_compile_options(main_lib INTERFACE -fno-common)
-endif()
-
 check_c_compiler_flag(-fdiagnostics-color=auto HAS_DIAG_COLOR_FLAG)
 if(HAS_DIAG_COLOR_FLAG)
   if(CMAKE_GENERATOR MATCHES "Ninja")