diff --git a/litex/build/lattice/diamond.py b/litex/build/lattice/diamond.py
index e3f91133f..cf44d096b 100644
--- a/litex/build/lattice/diamond.py
+++ b/litex/build/lattice/diamond.py
@@ -68,8 +68,8 @@ def _build_tcl(device, sources, vincpaths, build_name):
     ]))
 
     # Add include paths
-    for path in vincpaths:
-        tcl.append("prj_impl option {include path} {\"" + path + "\"}")
+    vincpath = ';'.join(map(lambda x: x.replace('\\', '/'), vincpaths))
+    tcl.append("prj_impl option {include path} {\"" + vincpath + "\"}")
 
     # Add sources
     for filename, language, library in sources:
@@ -201,4 +201,4 @@ class LatticeDiamondToolchain:
         from_.attr.add("keep")
         to.attr.add("keep")
         if (to, from_) not in self.false_paths:
-            self.false_paths.add((from_, to))
\ No newline at end of file
+            self.false_paths.add((from_, to))