diff --git a/src/main/java/io/xlate/edi/internal/stream/tokenization/Dialect.java b/src/main/java/io/xlate/edi/internal/stream/tokenization/Dialect.java
index cdf11e68..5cdae9c5 100644
--- a/src/main/java/io/xlate/edi/internal/stream/tokenization/Dialect.java
+++ b/src/main/java/io/xlate/edi/internal/stream/tokenization/Dialect.java
@@ -31,7 +31,7 @@ public abstract class Dialect {
     protected char elementRepeater;
 
     protected boolean initialized;
-    protected boolean rejected;
+    protected String rejectionMessage;
 
     protected String transactionType;
     protected String transactionVersionString;
@@ -90,7 +90,11 @@ public boolean isConfirmed() {
     }
 
     public boolean isRejected() {
-        return rejected;
+        return rejectionMessage != null;
+    }
+
+    public String getRejectionMessage() {
+        return rejectionMessage;
     }
 
     /**
diff --git a/src/main/java/io/xlate/edi/internal/stream/tokenization/EDIFACTDialect.java b/src/main/java/io/xlate/edi/internal/stream/tokenization/EDIFACTDialect.java
index 472cc0c8..cb04d0e0 100644
--- a/src/main/java/io/xlate/edi/internal/stream/tokenization/EDIFACTDialect.java
+++ b/src/main/java/io/xlate/edi/internal/stream/tokenization/EDIFACTDialect.java
@@ -100,6 +100,7 @@ boolean initialize(CharacterSet characters) {
             characters.setClass(segmentDelimiter, CharacterClass.SEGMENT_DELIMITER);
             initialized = true;
         } else {
+            rejectionMessage = "Unable to obtain version from EDIFACT header segment";
             initialized = false;
         }
 
@@ -189,7 +190,7 @@ boolean processInterchangeHeader(CharacterSet characters, char value) {
              */
             characters.setClass(elementDelimiter, CharacterClass.ELEMENT_DELIMITER);
         } else if (segmentDelimiter == value) {
-            rejected = !initialize(characters);
+            initialize(characters);
             return isConfirmed();
         }
 
@@ -232,7 +233,7 @@ boolean processServiceStringAdvice(CharacterSet characters, char value) {
                 header.deleteCharAt(index--);
             } else if (isIndexBeyondUNBFirstElement()) {
                 if (value == elementDelimiter || value == segmentDelimiter) {
-                    rejected = !initialize(characters);
+                    initialize(characters);
                     proceed = isConfirmed();
                 }
             } else if (value == 'B') {
diff --git a/src/main/java/io/xlate/edi/internal/stream/tokenization/Lexer.java b/src/main/java/io/xlate/edi/internal/stream/tokenization/Lexer.java
index 07e2aa7a..c0f2b808 100644
--- a/src/main/java/io/xlate/edi/internal/stream/tokenization/Lexer.java
+++ b/src/main/java/io/xlate/edi/internal/stream/tokenization/Lexer.java
@@ -185,7 +185,7 @@ public void parse() throws IOException, EDIException {
             CharacterClass clazz = characters.getClass(input);
             previous = state;
             state = State.transition(state, dialect, clazz);
-            LOGGER.finer(() -> String.format("State %s(%s, %s) -> %s", previous, clazz, Dialect.getStandard(dialect), state));
+            LOGGER.finer(() -> String.format("%s + (%s, '%s', %s) -> %s", previous, Dialect.getStandard(dialect), (char) input, clazz, state));
 
             switch (state) {
             case INITIAL:
@@ -418,9 +418,10 @@ private boolean dialectConfirmed(State confirmed) throws EDIException {
         } else if (dialect.isRejected()) {
             buffer.clear();
             clearQueues();
+            String rejectionMessage = dialect.getRejectionMessage();
             dialect = null;
             state = State.INITIAL;
-            throw error(EDIException.INVALID_STATE, "Invalid header segment");
+            throw error(EDIException.INVALID_STATE, rejectionMessage);
         }
 
         return false;
diff --git a/src/main/java/io/xlate/edi/internal/stream/tokenization/TradacomsDialect.java b/src/main/java/io/xlate/edi/internal/stream/tokenization/TradacomsDialect.java
index a064c8c0..b8ce9bad 100644
--- a/src/main/java/io/xlate/edi/internal/stream/tokenization/TradacomsDialect.java
+++ b/src/main/java/io/xlate/edi/internal/stream/tokenization/TradacomsDialect.java
@@ -24,6 +24,7 @@ public class TradacomsDialect extends Dialect {
     public static final String MHD = "MHD";
 
     private static final String[] EMPTY = new String[0];
+    private static final int TRADACOMS_ELEMENT_OFFSET = 3;
 
     static final char DFLT_SEGMENT_TERMINATOR = '\'';
     static final char DFLT_DATA_ELEMENT_SEPARATOR = '+';
@@ -62,6 +63,7 @@ boolean initialize(CharacterSet characters) {
             initialized = true;
             characters.setClass(segmentDelimiter, CharacterClass.SEGMENT_DELIMITER);
         } else {
+            rejectionMessage = "Unable to obtain version from TRADACOMS header segment";
             initialized = false;
         }
 
@@ -97,7 +99,11 @@ public boolean appendHeader(CharacterSet characters, char value) {
         case 0:
             header = new StringBuilder();
             break;
-        case 3:
+        case TRADACOMS_ELEMENT_OFFSET:
+            if (value != segmentTagTerminator) {
+                rejectionMessage = String.format("Expected TRADACOMS segment tag delimiter '%s', but found '%s'", segmentTagTerminator, value);
+                return false;
+            }
             /*
              * TRADACOMS delimiters are fixed. Do not set the element delimiter
              * until after the segment tag has been passed to prevent triggering
@@ -124,7 +130,7 @@ public boolean appendHeader(CharacterSet characters, char value) {
 
     boolean processInterchangeHeader(CharacterSet characters, char value) {
         if (segmentDelimiter == value) {
-            rejected = !initialize(characters);
+            initialize(characters);
             return isConfirmed();
         }
 
diff --git a/src/main/java/io/xlate/edi/internal/stream/tokenization/X12Dialect.java b/src/main/java/io/xlate/edi/internal/stream/tokenization/X12Dialect.java
index cb1dc574..66025aa7 100644
--- a/src/main/java/io/xlate/edi/internal/stream/tokenization/X12Dialect.java
+++ b/src/main/java/io/xlate/edi/internal/stream/tokenization/X12Dialect.java
@@ -80,6 +80,7 @@ boolean initialize(CharacterSet characters) {
 
         for (int i = 0, m = X12_ISA_LENGTH; i < m; i++) {
             if (ELEMENT == header[i] && X12_ISA_TOKENS[e++] != i) {
+                rejectionMessage = String.format("Unexpected element delimiter value '%s' in X12 header position %d", ELEMENT, i + 1);
                 return false;
             }
         }
@@ -150,7 +151,7 @@ public boolean appendHeader(CharacterSet characters, char value) {
         boolean proceed = true;
 
         if (index == X12_SEGMENT_OFFSET) {
-            rejected = !initialize(characters);
+            initialize(characters);
             proceed = isConfirmed();
         }
 
diff --git a/src/test/java/io/xlate/edi/internal/stream/StaEDIStreamReaderTest.java b/src/test/java/io/xlate/edi/internal/stream/StaEDIStreamReaderTest.java
index 218687bf..86c043ba 100644
--- a/src/test/java/io/xlate/edi/internal/stream/StaEDIStreamReaderTest.java
+++ b/src/test/java/io/xlate/edi/internal/stream/StaEDIStreamReaderTest.java
@@ -1939,4 +1939,47 @@ void testDecimalScaleAvailableFromSchema() throws EDISchemaException, IOExceptio
 
         assertEquals(new BigDecimal("2554.38"), tds01);
     }
+
+    /**
+     * Original issue: https://github.com/xlate/staedi/issues/174
+     *
+     * @throws Exception
+     */
+    @Test
+    void testOtherDialectTerminalSegmentsIgnored_Issue174() throws Exception {
+        EDIInputFactory factory = EDIInputFactory.newFactory();
+        factory.setProperty(EDIInputFactory.EDI_VALIDATE_CONTROL_STRUCTURE, true);
+        factory.setProperty(EDIInputFactory.EDI_VALIDATE_CONTROL_CODE_VALUES, false);
+        EDIStreamReader reader = factory.createEDIStreamReader(getClass().getResourceAsStream("/EDIFACT/issue174/other_dialect_term_segments.edi"));
+        List<Object> unexpected = new ArrayList<>();
+
+        try {
+            while (reader.hasNext()) {
+                switch (reader.next()) {
+                case SEGMENT_ERROR:
+                case ELEMENT_OCCURRENCE_ERROR:
+                case ELEMENT_DATA_ERROR:
+                    unexpected.add(reader.getErrorType());
+                    break;
+                default:
+                    break;
+                }
+            }
+        } catch (Exception e) {
+            unexpected.add(e);
+        } finally {
+            reader.close();
+        }
+
+        assertEquals(0, unexpected.size());
+    }
+
+    @Test
+    void testTRADACOMS_IncorrectSegmentTagDelimiterIsInvalid() throws Exception {
+        EDIInputFactory factory = EDIInputFactory.newFactory();
+        EDIStreamReader reader = factory.createEDIStreamReader(getClass().getResourceAsStream("/TRADACOMS/order-wrong-segment-tag-delimiter.edi"));
+        List<Object> unexpected = new ArrayList<>();
+        EDIStreamException thrown = assertThrows(EDIStreamException.class, () -> reader.next());
+        assertTrue(thrown.getMessage().contains("Expected TRADACOMS segment tag delimiter"));
+    }
 }
diff --git a/src/test/resources/EDIFACT/issue174/other_dialect_term_segments.edi b/src/test/resources/EDIFACT/issue174/other_dialect_term_segments.edi
new file mode 100644
index 00000000..f3ea5489
--- /dev/null
+++ b/src/test/resources/EDIFACT/issue174/other_dialect_term_segments.edi
@@ -0,0 +1,6 @@
+UNB+UNOA:3+005435656:1+006415160:1+210220:1605+00000000000001'
+UNH+00000000000001+CUSTOM:D:97B:UN'
+IEA+1:525'
+END+1:525'
+UNT+24+00000000000001'
+UNZ+1+00000000000001'
diff --git a/src/test/resources/TRADACOMS/order-wrong-segment-tag-delimiter.edi b/src/test/resources/TRADACOMS/order-wrong-segment-tag-delimiter.edi
new file mode 100644
index 00000000..56a119aa
--- /dev/null
+++ b/src/test/resources/TRADACOMS/order-wrong-segment-tag-delimiter.edi
@@ -0,0 +1,18 @@
+STX+ANA:1+5000000000000:SOME STORES LTD+5010000000000:SUPPLIER UK LTD+070315:130233+000007+PASSW+ORDHDR+B'
+MHD+1+ORDHDR:9'
+TYP+0430+NEW-ORDERS'
+SDT+5010000000000:000030034'
+CDT+5000000000000'
+FIL+1630+1+070315'
+MTR+6'
+MHD+2+ORDERS:9'
+CLO+5000000000283:89828+EAST SOMEWHERE DEPOT'
+ORD+70970::070315'
+DIN+070321++0000'
+OLD+1+5010210000000++:00893592+12+60++++CRUSTY ROLLS:4 PACK'
+OTR+1'
+MTR+7'
+MHD+3+ORDTLR:9'
+OFT+1'
+MTR+3'
+END+3'