diff --git a/src/support/os_cygwin.cpp b/src/support/os_cygwin.cpp
index 3ab910fedd..1bfffdc828 100644
--- a/src/support/os_cygwin.cpp
+++ b/src/support/os_cygwin.cpp
@@ -185,7 +185,7 @@ bool path_prefix_is(string & path, string const & pre, path_case how)
 	if (i + 1 != p2.length())
 		return false;
 
-	if (!prefixIs(path, pre) && how == CASE_ADJUSTED)
+	if (how == CASE_ADJUSTED && !prefixIs(path, pre))
 		path = to_utf8(p2 + p1.substr(i + 1, p1.length() - i + 1));
 
 	return true;
diff --git a/src/support/os_unix.cpp b/src/support/os_unix.cpp
index 976fcf75e8..15c5e63369 100644
--- a/src/support/os_unix.cpp
+++ b/src/support/os_unix.cpp
@@ -98,7 +98,7 @@ bool path_prefix_is(string & path, string const & pre, path_case how)
 	if (i + 1 != p2.length())
 		return false;
 
-	if (!prefixIs(path, pre) && how == CASE_ADJUSTED)
+	if (how == CASE_ADJUSTED && !prefixIs(path, pre))
 		path = to_utf8(p2 + p1.substr(i + 1, p1.length() - i + 1));
 
 	return true;
diff --git a/src/support/os_win32.cpp b/src/support/os_win32.cpp
index 732cdc55ab..722895b1cf 100644
--- a/src/support/os_win32.cpp
+++ b/src/support/os_win32.cpp
@@ -216,7 +216,7 @@ bool path_prefix_is(string & path, string const & pre, path_case how)
 	if (i + 1 != p2.length())
 		return false;
 
-	if (!prefixIs(path, pre) && how == CASE_ADJUSTED)
+	if (how == CASE_ADJUSTED && !prefixIs(path, pre))
 		path = to_utf8(p2 + p1.substr(i + 1, p1.length() - i + 1));
 
 	return true;