diff --git a/SourceGen/Anattrib.cs b/SourceGen/Anattrib.cs
index ad85e55..944bf44 100644
--- a/SourceGen/Anattrib.cs
+++ b/SourceGen/Anattrib.cs
@@ -218,8 +218,8 @@ namespace SourceGen {
         public int Address { get; set; }
 
         /// <summary>
-        /// Instructions: length of the instruction (for InstrStart).  If a FormatDescriptor
-        ///   is assigned, the length must match.
+        /// Instructions: length of the instruction (for InstrStart).  If a FormatDescriptor is
+        ///   assigned, the length must match, or the dfd will be ignored.
         /// Inline data: FormatDescriptor length, or zero if no descriptor is defined.
         /// Data: FormatDescriptor length, or zero if no descriptor is defined.
         /// 
diff --git a/SourceGen/DisasmProject.cs b/SourceGen/DisasmProject.cs
index c61fd26..260cf53 100644
--- a/SourceGen/DisasmProject.cs
+++ b/SourceGen/DisasmProject.cs
@@ -581,6 +581,58 @@ namespace SourceGen {
             return sb.ToString();
         }
 
+        /// <summary>
+        /// Checks some stuff.  Problems are handled with assertions, so this is only
+        /// useful in debug builds.
+        /// </summary>
+        public void Validate() {
+            // Confirm that we can walk through the file, stepping directly from the start
+            // of one thing to the start of the next.
+            int offset = 0;
+            while (offset < mFileData.Length) {
+                Anattrib attr = mAnattribs[offset];
+                bool thisIsCode = attr.IsInstructionStart;
+                Debug.Assert(attr.IsStart);
+                Debug.Assert(attr.Length != 0);
+                offset += attr.Length;
+
+                // Sometimes embedded instructions continue past the "outer" instruction,
+                // usually because we're misinterpreting the code.  We need to deal with
+                // that here.
+                int extraInstrBytes = 0;
+                while (offset < mFileData.Length && mAnattribs[offset].IsInstruction &&
+                        !mAnattribs[offset].IsInstructionStart) {
+                    extraInstrBytes++;
+                    offset++;
+                }
+
+                // Make sure the extra code bytes were part of an instruction.  Otherwise it
+                // means we moved from the end of a data area to the middle of an instruction,
+                // which is very bad.
+                Debug.Assert(extraInstrBytes == 0 || thisIsCode);
+
+                //if (extraInstrBytes > 0) { Debug.WriteLine("EIB=" + extraInstrBytes); }
+                // Max instruction len is 4, so the stray part must be shorter.
+                Debug.Assert(extraInstrBytes < 4);
+            }
+            Debug.Assert(offset == mFileData.Length);
+
+            // Confirm that all bytes are tagged as code, data, or inline data.  The Asserts
+            // in Anattrib should confirm that nothing is tagged as more than one thing.
+            for (offset = 0; offset < mAnattribs.Length; offset++) {
+                Anattrib attr = mAnattribs[offset];
+                Debug.Assert(attr.IsInstruction || attr.IsInlineData || attr.IsData);
+            }
+
+            // Confirm that there are no Default format entries in OperandFormats.
+            foreach (KeyValuePair<int, FormatDescriptor> kvp in OperandFormats) {
+                Debug.Assert(kvp.Value.FormatType != FormatDescriptor.Type.Default);
+                Debug.Assert(kvp.Value.FormatType != FormatDescriptor.Type.REMOVE);
+            }
+        }
+
+        #region Analysis
+
         /// <summary>
         /// Analyzes the file data.  This is the main entry point for code/data analysis.
         /// </summary>
@@ -1298,55 +1350,10 @@ namespace SourceGen {
             });
         }
 
-        /// <summary>
-        /// Checks some stuff.  Problems are handled with assertions, so this is only
-        /// useful in debug builds.
-        /// </summary>
-        public void Validate() {
-            // Confirm that we can walk through the file, stepping directly from the start
-            // of one thing to the start of the next.
-            int offset = 0;
-            while (offset < mFileData.Length) {
-                Anattrib attr = mAnattribs[offset];
-                bool thisIsCode = attr.IsInstructionStart;
-                Debug.Assert(attr.IsStart);
-                Debug.Assert(attr.Length != 0);
-                offset += attr.Length;
+        #endregion Analysis
 
-                // Sometimes embedded instructions continue past the "outer" instruction,
-                // usually because we're misinterpreting the code.  We need to deal with
-                // that here.
-                int extraInstrBytes = 0;
-                while (offset < mFileData.Length && mAnattribs[offset].IsInstruction &&
-                        !mAnattribs[offset].IsInstructionStart) {
-                    extraInstrBytes++;
-                    offset++;
-                }
 
-                // Make sure the extra code bytes were part of an instruction.  Otherwise it
-                // means we moved from the end of a data area to the middle of an instruction,
-                // which is very bad.
-                Debug.Assert(extraInstrBytes == 0 || thisIsCode);
-
-                //if (extraInstrBytes > 0) { Debug.WriteLine("EIB=" + extraInstrBytes); }
-                // Max instruction len is 4, so the stray part must be shorter.
-                Debug.Assert(extraInstrBytes < 4);
-            }
-            Debug.Assert(offset == mFileData.Length);
-
-            // Confirm that all bytes are tagged as code, data, or inline data.  The Asserts
-            // in Anattrib should confirm that nothing is tagged as more than one thing.
-            for (offset = 0; offset < mAnattribs.Length; offset++) {
-                Anattrib attr = mAnattribs[offset];
-                Debug.Assert(attr.IsInstruction || attr.IsInlineData || attr.IsData);
-            }
-
-            // Confirm that there are no Default format entries in OperandFormats.
-            foreach (KeyValuePair<int, FormatDescriptor> kvp in OperandFormats) {
-                Debug.Assert(kvp.Value.FormatType != FormatDescriptor.Type.Default);
-                Debug.Assert(kvp.Value.FormatType != FormatDescriptor.Type.REMOVE);
-            }
-        }
+        #region Change Management
 
         /// <summary>
         /// Generates a ChangeSet that merges the FormatDescriptors in the new list into
@@ -1978,6 +1985,8 @@ namespace SourceGen {
             }
         }
 
+        #endregion Change Management
+
         /// <summary>
         /// Finds a label by name.  SymbolTable must be populated.
         /// </summary>
diff --git a/SourceGen/MainController.cs b/SourceGen/MainController.cs
index 8205017..8c2e969 100644
--- a/SourceGen/MainController.cs
+++ b/SourceGen/MainController.cs
@@ -3267,6 +3267,12 @@ namespace SourceGen {
                 // If the descriptor has a weak reference to an unknown symbol, should we
                 // call that out here?
                 sb.AppendFormat(Res.Strings.INFO_FD_SUM_FMT, dfd.ToUiString());
+
+                // If the format descriptor for an instruction has the wrong length, it will
+                // be ignored.  Call that out.
+                if (attr.IsInstructionStart && attr.Length != dfd.Length) {
+                    sb.AppendFormat(" [incorrect format length]");
+                }
             }
             sb.Append("\r\n");