diff --git a/lcl/interfaces/qt5/cbindings/Qt5Pas.pro b/lcl/interfaces/qt5/cbindings/Qt5Pas.pro
index 7283b115a8..e835e2b93a 100644
--- a/lcl/interfaces/qt5/cbindings/Qt5Pas.pro
+++ b/lcl/interfaces/qt5/cbindings/Qt5Pas.pro
@@ -25,7 +25,7 @@ TEMPLATE = lib
 VPATH = src
 MOC_DIR = tmp
 OBJECTS_DIR = tmp
-QMAKE_CXXFLAGS += -Wfatal-errors
+QMAKE_CXXFLAGS += -Wfatal-errors -fvisibility=hidden
 
 # Match Intel x86_64 i686 i586 i386 x86 ...
 is86 = $$find(QMAKE_HOST.arch, ".*86")
diff --git a/lcl/interfaces/qt5/cbindings/src/pascalbind.h b/lcl/interfaces/qt5/cbindings/src/pascalbind.h
index 096de7fd20..8d7c94d33f 100644
--- a/lcl/interfaces/qt5/cbindings/src/pascalbind.h
+++ b/lcl/interfaces/qt5/cbindings/src/pascalbind.h
@@ -30,7 +30,7 @@
 #if defined(__WIN32__)
 #define C_EXPORT extern "C" __declspec( dllexport )
 #else
-#define C_EXPORT extern "C"
+#define C_EXPORT extern "C" __attribute__(( visibility("default") ))
 #endif
 
 #ifdef __WIN32__
diff --git a/lcl/interfaces/qt6/cbindings/Qt6Pas.pro b/lcl/interfaces/qt6/cbindings/Qt6Pas.pro
index 50b69f2f14..22fb9db5ea 100644
--- a/lcl/interfaces/qt6/cbindings/Qt6Pas.pro
+++ b/lcl/interfaces/qt6/cbindings/Qt6Pas.pro
@@ -25,7 +25,7 @@ TEMPLATE = lib
 VPATH = src
 MOC_DIR = tmp
 OBJECTS_DIR = tmp
-QMAKE_CXXFLAGS += -Wfatal-errors
+QMAKE_CXXFLAGS += -Wfatal-errors -fvisibility=hidden
 
 # Match Intel x86_64 i686 i586 i386 x86 ...
 is86 = $$find(QMAKE_HOST.arch, ".*86")
diff --git a/lcl/interfaces/qt6/cbindings/src/pascalbind.h b/lcl/interfaces/qt6/cbindings/src/pascalbind.h
index 6f5b4b7aa3..6e8df8e17c 100644
--- a/lcl/interfaces/qt6/cbindings/src/pascalbind.h
+++ b/lcl/interfaces/qt6/cbindings/src/pascalbind.h
@@ -29,7 +29,7 @@
 #if defined(WIN32) || defined(__WIN32) || defined(__WIN32__)
 #define C_EXPORT extern "C" __declspec( dllexport )
 #else
-#define C_EXPORT extern "C"
+#define C_EXPORT extern "C" __attribute__(( visibility("default") ))
 #endif
 
 #if defined(WIN32) || defined(__WIN32) || defined(__WIN32__)