diff --git a/ostap/CMakeLists.txt b/ostap/CMakeLists.txt
index 76c35e0a..01d09546 100644
--- a/ostap/CMakeLists.txt
+++ b/ostap/CMakeLists.txt
@@ -186,14 +186,14 @@ if  ( ${PYTHON_VERSION} VERSION_GREATER_EQUAL "3.3"  )
 if  ( ${PYTHON_VERSION} VERSION_LESS_EQUAL "3.6" )
    find_python_module ( berkeleydb QUIET )
    if ( NOT ${PY_berkeleydb_FOUND} )
-     execute_process(COMMAND ${PYTHON_EXECUTABLE} -m pip install 'berkeleydb=18.1.4' ${PIP_ARGS})
+     execute_process(COMMAND ${PYTHON_EXECUTABLE} -m pip install 'berkeleydb==18.1.4' ${PIP_ARGS})
    endif()
 endif()
 
 if  ( ${PYTHON_VERSION} VERSION_LESS_EQUAL "3.7" )
    find_python_module ( berkeleydb QUIET )
    if ( NOT ${PY_berkeleydb_FOUND} )
-     execute_process(COMMAND ${PYTHON_EXECUTABLE} -m pip install 'berkeleydb=18.1.6' ${PIP_ARGS})
+     execute_process(COMMAND ${PYTHON_EXECUTABLE} -m pip install 'berkeleydb==18.1.6' ${PIP_ARGS})
    endif()
 endif()