Hi all, I'm getting a strange error when I run my rules deployed from Guvnor. Here's the rule: WHEN Fact1 [f1] Flag1 = false Flag2 = false Fact2 [f2] KeyField = f1.KeyField THEN f1.Flag2 = true; update(f1); f2.count1 = f2.count1 - 1; f2.count2 = f2.count2 - 1; f2.count3 = f2.count3 - 1; f2.count4 = f2.count4 - 1; f2.count5 = f2.count5 - 1; update(f2); I get the following error in my console when I run: Exception in readKnowledgeBase: [Error: illegal use of operator: PROJECT] [Near : {... Unknown ....}] ^ [Line: 1, Column: 0] If I remove the second update, it runs without error (but my rules dependent on the updated f2 don't work). I'm doing this in the Guided Editor. I've tried both "Modify the values of f2" and doing the update as free form DRL ("update(f2);"). As listed above, if I put a print between the last assignment and the update, I get the print results before the error. If I put the print last, I never see it, so I'm 99.9% certain it is choking on my update. Version Specifics: - Guvnor 5.0.1 - Drools 5.0.1 - JBoss 4.2.3.GA Any help/guidance would be appreciated!