diff --git a/src/CMakeLists.txt b/src/CMakeLists.txt
index c615baf3..c8e43468 100644
--- a/src/CMakeLists.txt
+++ b/src/CMakeLists.txt
@@ -23,7 +23,7 @@ if(OPFLOW_ENABLE_MODULE)
     # ----------------------------------------------------------------------------
     add_library(opflow)
 
-    target_compile_definitions(opflow PUBLIC OPFLOW_USE_MODULE)
+    target_compile_definitions(opflow PRIVATE OPFLOW_USE_MODULE)
     set_property(TARGET opflow PROPERTY CXX_SCAN_FOR_MODULES ON)
     target_sources(opflow
         PUBLIC FILE_SET CXX_MODULES
@@ -42,7 +42,7 @@ if(OPFLOW_ENABLE_MODULE)
         FILE_SET HEADERS DESTINATION ${CMAKE_INSTALL_INCLUDEDIR})
 else()
     # ----------------------------------------------------------------------------
-    # C++20 header only version
+    # C++26 header only version
     # ----------------------------------------------------------------------------
     add_library(opflow INTERFACE)
     set_property(TARGET opflow PROPERTY CXX_SCAN_FOR_MODULES OFF)
@@ -59,6 +59,13 @@ else()
 endif()
 add_library(opflow::opflow ALIAS opflow)
 
+# Set OPFLOW_TARGET_SCOPE based on module enable status
+if(OPFLOW_ENABLE_MODULE)
+    set(OPFLOW_TARGET_SCOPE PUBLIC)
+else()
+    set(OPFLOW_TARGET_SCOPE INTERFACE)
+endif()
+
 # Create & include the version header
 configure_file(${CMAKE_CURRENT_LIST_DIR}/../cmake/Version.hpp.in ${CMAKE_BINARY_DIR}/Version.hpp @ONLY)
 
@@ -120,3 +127,25 @@ target_link_options(opflow
     INTERFACE $<$<BOOL:${OPFLOW_SANITIZE_LEAK}>: -fsanitize=leak>
     INTERFACE $<$<BOOL:${OPFLOW_SANITIZE_THREAD}>: -fsanitize=thread>
     INTERFACE $<$<BOOL:${OPFLOW_SANITIZE_UB}>: -fsanitize=undefined>)
+
+# ----------------------------------------------------------------------------
+# Compiler warnings
+# ----------------------------------------------------------------------------
+# Enable strict warnings and treat warnings as errors by default
+
+if(CMAKE_CXX_COMPILER_ID MATCHES "GNU" OR CMAKE_CXX_COMPILER_ID MATCHES "Clang")
+    target_compile_options(opflow ${OPFLOW_TARGET_SCOPE}
+        -Wall
+        -Wextra
+        -Werror
+        # Suppress possible ABI warning from compiler upgrades
+        -Wno-psabi
+    )
+endif()
+# MSVC-specific warnings
+if(MSVC)
+    target_compile_options(opflow ${OPFLOW_TARGET_SCOPE}
+        /W4
+        /WX
+    )
+endif()