diff --git a/src/processor.ts b/src/processor.ts
index ebe77ad..0460d2b 100644
--- a/src/processor.ts
+++ b/src/processor.ts
@@ -274,6 +274,52 @@ parse("", {});
   ];
 }
 
+function sourceMapMessages(
+  messages: ESlint.Linter.LintMessage[],
+  map: SourceChain
+): ESlint.Linter.LintMessage[] {
+  const res: ESlint.Linter.LintMessage[] = [];
+  for (const msg of messages) {
+    debug("Before: %o", msg);
+    const start = map.originalLocation({
+      line: msg.line,
+      column: msg.column - 1, // Map is 0-based cols
+    }, Bias.ERROR);
+    debug("Start: %o", start);
+    if (start) {
+      msg.line = start.line;
+      msg.column = start.column + 1; // Message is 1-based cols
+    } else {
+      debug("Cound't find start location column: %d line %d", msg.line, msg.column);
+      continue;
+    }
+
+    const end
+      = (typeof msg.endLine === "number") && (typeof msg.endColumn === "number")
+        ? map.originalLocation({
+          line: msg.endLine,
+          column: msg.endColumn - 1,  // Map is 0-based cols
+        }, Bias.GREATEST_LOWER_BOUND)
+        : null;
+    if (end) {
+      msg.endLine = end.line;
+      msg.endColumn = end.column + 1; // Message is 1-based cols
+    } else {
+      debug("Cound't find end location column: %d line %d", msg.endLine, msg.endColumn);
+      continue;
+    }
+    if (msg.fix) {
+      msg.fix.range = [
+        map.originalOffset(msg.fix.range[0], Bias.LEAST_UPPER_BOUND),
+        map.originalOffset(msg.fix.range[1], Bias.GREATEST_LOWER_BOUND),
+      ];
+    }
+    debug("After: %o", msg);
+    res.push(msg);
+  }
+  return res;
+}
+
 /**
  * Put all of the line/column numbers back into the original file.
  *
@@ -292,45 +338,7 @@ export function postprocess(
 
   return [
     ...messages[0],
-    ...messages[1].map(msg => {
-      debug("Before: %o", msg);
-      const start = map.originalLocation({
-        line: msg.line,
-        column: msg.column - 1, // Map is 0-based cols
-      }, Bias.LEAST_UPPER_BOUND);
-      if (start) {
-        msg.line = start.line;
-        msg.column = start.column + 1; // Message is 1-based cols
-      } else {
-        msg.line = 1;
-        msg.column = 1;
-        debug("Cound't find start location column: %d line %d", msg.line, msg.column);
-      }
-
-      const end
-        = (typeof msg.endLine === "number") && (typeof msg.endColumn === "number")
-          ? map.originalLocation({
-            line: msg.endLine,
-            column: msg.endColumn - 1,  // Map is 0-based cols
-          }, Bias.GREATEST_LOWER_BOUND)
-          : null;
-      if (end) {
-        msg.endLine = end.line;
-        msg.endColumn = end.column + 1; // Message is 1-based cols
-      } else {
-        debug("Cound't find end location column: %d line %d", msg.endLine, msg.endColumn);
-        msg.endLine = undefined;
-        msg.endColumn = undefined;
-      }
-      if (msg.fix) {
-        msg.fix.range = [
-          map.originalOffset(msg.fix.range[0], Bias.LEAST_UPPER_BOUND),
-          map.originalOffset(msg.fix.range[1], Bias.GREATEST_LOWER_BOUND),
-        ];
-      }
-      debug("After: %o", msg);
-      return msg;
-    }),
+    ...sourceMapMessages(messages[1], map),
   ];
 }
 
diff --git a/src/sourcechain.ts b/src/sourcechain.ts
index 6d433c7..e844fdb 100644
--- a/src/sourcechain.ts
+++ b/src/sourcechain.ts
@@ -33,6 +33,10 @@ export enum Bias {
    * *next* non-boilerplate block.
    */
   GREATEST_LOWER_BOUND = 1,
+  /**
+   * If the position specified is in the boilerplate text, return null.
+   */
+  ERROR = 2,
 }
 
 /**
@@ -170,6 +174,9 @@ export class SourceChain {
           // Now we're sure we've got the right block
           if (!block.loc) {
             // But it's in the generated section.
+            if (bias === Bias.ERROR) {
+              return null;
+            }
             // Do we want the end of the previous block?
             if ((bias === Bias.LEAST_UPPER_BOUND) && prev?.loc) {
               if (prev.tail) {
diff --git a/test/processor.test.js b/test/processor.test.js
index 05ab0a1..85b4b65 100644
--- a/test/processor.test.js
+++ b/test/processor.test.js
@@ -20,45 +20,58 @@ foo
   });
 
   it("post-processes", () => {
-    const messages = [[], [{
-      ruleId: "semi",
-      severity: 2,
-      message: "Semicolon required",
-      line: 300,
-      column: 26,
-      endLine: 4,
-      endColumn: 1,
-    }, {
-      ruleId: "no-unused-vars",
-      severity: 2,
-      message: "'o' is defined but never used.",
-      line: 31,
-      column: 19,
-      nodeType: "Identifier",
-      messageId: "unusedVar",
-      endLine: 31,
-      endColumn: 20,
-    }, {
-      ruleId: "no-unused-vars",
-      severity: 2,
-      message: "'t' is defined but never used.",
-      line: 31,
-      column: 22,
-      nodeType: "Identifier",
-      messageId: "unusedVar",
-      endLine: 31,
-      endColumn: 23,
-    }, {
-      ruleId: "example",
-      severity: 2,
-      message: "No end in sight",
-      line: 31,
-      column: 22,
-      nodeType: "none",
-    }]];
+    const messages = [[], [
+      {
+        ruleId: "semi",
+        severity: 2,
+        message: "Semicolon required",
+        line: 3,
+        column: 24,
+        endLine: 4,
+        endColumn: 1,
+      },
+      {
+        ruleId: "no-unused-vars",
+        severity: 2,
+        message: "'o' is defined but never used.",
+        line: 31,
+        column: 5,
+        nodeType: "Identifier",
+        messageId: "unusedVar",
+        endLine: 31,
+        endColumn: 6,
+      },
+      {
+        ruleId: "no-unused-vars",
+        severity: 2,
+        message: "'t' is defined but never used.",
+        line: 32,
+        column: 5,
+        nodeType: "Identifier",
+        messageId: "unusedVar",
+        endLine: 32,
+        endColumn: 6,
+      },
+      {
+        ruleId: "example",
+        severity: 2,
+        message: "No end in sight",
+        line: 32,
+        column: 5,
+        nodeType: "none",
+      },
+      {
+        ruleId: "example2",
+        severity: 2,
+        message: "Invalid start",
+        line: 1,
+        column: 1,
+        nodeType: "none",
+      },
+    ]];
 
     const mapped = processor.postprocess(messages, "processor.peggy");
-    assert.equal(mapped.length, messages[1].length);
+    assert.equal(mapped.length, messages[1].length - 2);
 
     assert.throws(() => processor.postprocess(messages, "NOT_VALID"), /Map not found/);
   });
@@ -87,8 +100,8 @@ num = n:$[0-9]+ { return parseInt(n, BASE); }
         ruleId: "semi",
         severity: 2,
         message: "Missing semicolon.",
-        line: 24,
-        column: 34,
+        line: 3,
+        column: 32,
         nodeType: "VariableDeclaration",
         messageId: "missingSemi",
         endLine: 25,