diff --git a/Programs/testPrograms/stringKeyword.asm b/Programs/testPrograms/stringKeyword.asm
new file mode 100644
index 0000000..60e3ccc
--- /dev/null
+++ b/Programs/testPrograms/stringKeyword.asm
@@ -0,0 +1,48 @@
+; A program whose data contains the names of directives.
+;
+; The quotes are gone by the time the assembler looks at a token, so "#Program" written as
+; a string looked exactly like the directive. It was read as one: the segment silently
+; changed in the middle of the Data Segment, the string's nine bytes were charged to the
+; Program cursor instead, and every label defined after it came out nine bytes wrong. The
+; file still had a valid header and a plausible length, so nothing said a word - the only
+; symptom was a program that jumped into the middle of an instruction.
+;
+; This is the fourth of that family. A string spelling a mnemonic assembled as that
+; instruction, a string beginning with a zero was rejected as a malformed literal, a string
+; in the Program Segment was discarded in silence, and now this.
+;
+; It came up because an assembler written FOR this machine has to compare tokens against
+; the directive names, so it necessarily has them in its data. Nothing else ever did.
+;
+; What it checks: that the strings survive as strings, and that a label defined after them
+; still points where it should. Everything after Directives would shift if the bug came
+; back, so printing Message is the test.
+;
+; Written by Anachronaut
+
+#Program
+
+start:
+  SETD.0 Directives
+  CALL show
+  SETD.0 Message
+  CALL show
+  HALT
+
+show:
+  LDA.0
+  BRA showDone
+  OUTA 0x00
+  INCD.0
+  BRI show
+showDone:
+  RET
+
+#Data
+
+Directives:
+"#Program #Data #Include #Vectors #Base #Align #Reserve
+"
+Message:
+"and a label after them still points at itself
+"
diff --git a/Source/Assembler/Assm-util.c b/Source/Assembler/Assm-util.c
index bad9434..921dde8 100644
--- a/Source/Assembler/Assm-util.c
+++ b/Source/Assembler/Assm-util.c
@@ -44,6 +44,19 @@ void toUppercase(char *str) {
 }
 
 int checkIfKeyword(intermediateElement *currentElement) {
+    // A string is never a keyword, however it is spelled. The quotes are gone by the time
+    // a token is looked at, so a program with "#Program" in its data - which is exactly
+    // what an assembler written for this machine needs, to compare tokens against - had
+    // the string read as the directive. The segment silently changed in the middle of the
+    // Data Segment, the string's nine bytes were charged to the Program cursor, and every
+    // label after it was nine bytes out while the file itself still looked well formed.
+    //
+    // This is the fourth of this family: the instruction check and the literal check both
+    // carry the same guard, for the same reason. It lives inside this one rather than at
+    // the call site so that it cannot be left off again.
+    if (currentElement->type == STRING) {
+        return 0;
+    }
     if (currentElement->token[0] == '#') {
         if (debug) printf("Token: %s is a keyword.\n", currentElement->token);
         currentElement->type = KEYWORD;
diff --git a/Tests/expected/stringKeyword.out b/Tests/expected/stringKeyword.out
new file mode 100644
index 0000000..c4cc509
--- /dev/null
+++ b/Tests/expected/stringKeyword.out
@@ -0,0 +1,4 @@
+#Program #Data #Include #Vectors #Base #Align #Reserve
+and a label after them still points at itself
+Execution halted.
+[exit 0]
diff --git a/Tests/manifest b/Tests/manifest
index 0d0e968..ea90ea0 100644
--- a/Tests/manifest
+++ b/Tests/manifest
@@ -387,6 +387,11 @@ diagUnbasedSegment   | testPrograms/diagnostics/unbasedSegment.asm | xfail | -
 lib-print            | Libraries/print.asm                | xfail    | -                  | -
 # These three call print.asm routines but have no #Include line at all. They are
 # only ever pulled in by printTest.asm, so they are not standalone programs.
+# A string that spells a directive is a string. The quotes are gone by the time a token is
+# looked at, so "#Program" in a program's data was read as the directive: the segment
+# changed in the middle of the Data Segment and every label after it came out nine bytes
+# wrong, in a file that still had a valid header and a plausible length.
+stringKeyword        | testPrograms/stringKeyword.asm     | run      | -                  | -
 printDecimalTest     | testPrograms/printDecimalTest.asm  | xfail    | -                  | -
 printDigitTest       | testPrograms/printDigitTest.asm    | xfail    | -                  | -
 printHexTest         | testPrograms/printHexTest.asm      | xfail    | -                  | -