diff --git a/Compiler/PCU/PCUReader.cs b/Compiler/PCU/PCUReader.cs
index 48a5cf4f2..8abcc9cc2 100644
--- a/Compiler/PCU/PCUReader.cs
+++ b/Compiler/PCU/PCUReader.cs
@@ -268,6 +268,7 @@ namespace PascalABCCompiler.PCU
                 if (NeedRecompiled())
                 {
                     CloseUnit();
+                    this.unit = null;
                     need = true;
                     return null; // return comp.RecompileUnit(FileName);
                 }
@@ -363,6 +364,7 @@ namespace PascalABCCompiler.PCU
                     if (already_compiled[used_unit_fname] == null)
                     {
                         var sub_u = pr.GetCompilationUnit(used_unit_fname, this.readDebugInfo);
+                        if (sub_u == null) return true;
                         this.unit.DirectInterfaceCompilationUnits.Add(sub_u.SemanticTree, sub_u);
                         this.unit.InterfaceUsedUnits.AddElement(sub_u.SemanticTree, pcu_file.incl_modules[i]);
                     }