diff --git a/external/CMakeLists.txt b/external/CMakeLists.txt
index ca2fe28a9..b0c83a257 100644
--- a/external/CMakeLists.txt
+++ b/external/CMakeLists.txt
@@ -784,12 +784,23 @@ if ((LINUX OR APPLE) AND (NOT LIBSIGMF_FOUND OR LIBSIGMF_EXTERNAL))
             <SOURCE_DIR>/external/flatbuffers/CMakeLists.txt
         COMMAND ${CMAKE_COMMAND} -E rm -f <SOURCE_DIR>/external/flatbuffers/CMakeLists.txt.bak
     )
+
+    set(LIBSIGMF_C_FLAGS "")
+    set(LIBSIGMF_CXX_FLAGS "")
+    if(LINUX)
+        set(LIBSIGMF_C_FLAGS "-O2")
+        set(LIBSIGMF_CXX_FLAGS "-O2")
+    endif()
+
     ExternalProject_Add(libsigmf
             GIT_REPOSITORY https://github.com/f4exb/libsigmf.git
             GIT_TAG ${LIBSIGMF_TAG}
             PREFIX "${EXTERNAL_BUILD_LIBRARIES}/libsigmf"
             INSTALL_DIR "${EXTERNAL_BUILD_LIBRARIES}"
-            CMAKE_ARGS ${COMMON_CMAKE_ARGS} -DCMAKE_INSTALL_PREFIX=<INSTALL_DIR>
+            CMAKE_ARGS ${COMMON_CMAKE_ARGS}
+            -DCMAKE_INSTALL_PREFIX=<INSTALL_DIR>
+            -DCMAKE_C_FLAGS=${LIBSIGMF_C_FLAGS}
+            -DCMAKE_CXX_FLAGS=${LIBSIGMF_CXX_FLAGS}
             UPDATE_DISCONNECTED TRUE
             PATCH_COMMAND ${LIBSIGMF_PATCH_COMMAND}
             BUILD_BYPRODUCTS "${LIBSIGMF_LIBRARIES}"
@@ -804,7 +815,7 @@ if ((LINUX OR APPLE) AND (NOT LIBSIGMF_FOUND OR LIBSIGMF_EXTERNAL))
         install(FILES "${LIBSIGMF_LIBRARIES}" DESTINATION "${INSTALL_LIB_DIR}")
         set(MACOS_EXTERNAL_LIBS_FIXUP "${MACOS_EXTERNAL_LIBS_FIXUP};${binary_dir}/")
     endif ()
-endif ((LINUX OR APPLE) AND (NOT LIBSIGMF_FOUND OR LIBSIGMF_EXTERNAL))
+endif ()
 
 # For APT demodulator
 if(ENABLE_CHANNELRX_DEMODAPT)