diff --git a/CMakeLists.txt b/CMakeLists.txt
index c16a137..8be3742 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -47,17 +47,18 @@ if(TARGET libzmq)
 elseif(BUILD_SHARED_LIBS)
     include(FindPkgConfig)
     pkg_check_modules(libzmq libzmq>=4.3 IMPORTED_TARGET)
-    # Debian sid includes a -isystem in the mit-krb package that, starting with pkg-config 0.29.2,
-    # breaks cmake's pkgconfig module because it stupidly thinks "-isystem" is a path, so if we find
-    # -isystem in the include dirs then hack it out.
-    get_property(zmq_inc TARGET PkgConfig::libzmq PROPERTY INTERFACE_INCLUDE_DIRECTORIES)
-    list(FIND zmq_inc "-isystem" broken_isystem)
-    if(NOT broken_isystem EQUAL -1)
-      list(REMOVE_AT zmq_inc ${broken_isystem})
-      set_property(TARGET PkgConfig::libzmq PROPERTY INTERFACE_INCLUDE_DIRECTORIES ${zmq_inc})
-    endif()
 
     if(libzmq_FOUND)
+        # Debian sid includes a -isystem in the mit-krb package that, starting with pkg-config 0.29.2,
+        # breaks cmake's pkgconfig module because it stupidly thinks "-isystem" is a path, so if we find
+        # -isystem in the include dirs then hack it out.
+        get_property(zmq_inc TARGET PkgConfig::libzmq PROPERTY INTERFACE_INCLUDE_DIRECTORIES)
+        list(FIND zmq_inc "-isystem" broken_isystem)
+        if(NOT broken_isystem EQUAL -1)
+          list(REMOVE_AT zmq_inc ${broken_isystem})
+          set_property(TARGET PkgConfig::libzmq PROPERTY INTERFACE_INCLUDE_DIRECTORIES ${zmq_inc})
+        endif()
+
         target_link_libraries(lokimq PUBLIC PkgConfig::libzmq)
     else()
         set(lokimq_build_static_libzmq ON)