diff --git a/src/locales/en/constants.ts b/src/locales/en/constants.ts
index 298b04ab..ae63c795 100644
--- a/src/locales/en/constants.ts
+++ b/src/locales/en/constants.ts
@@ -277,7 +277,7 @@ export const TIME_UNITS_NO_ABBR_PATTERN = repeatedTimeunitPattern(
     TIME_UNIT_CONNECTOR_PATTERN
 );
 
-export function parseTimeUnits(timeunitText): TimeUnits {
+export function parseTimeUnits(timeunitText): null | TimeUnits {
     const fragments = {};
     let remainingText = timeunitText;
     let match = SINGLE_TIME_UNIT_REGEX.exec(remainingText);
@@ -286,10 +286,16 @@ export function parseTimeUnits(timeunitText): TimeUnits {
         remainingText = remainingText.substring(match[0].length).trim();
         match = SINGLE_TIME_UNIT_REGEX.exec(remainingText);
     }
+    if (Object.keys(fragments).length == 0) {
+        return null;
+    }
     return fragments;
 }
 
 function collectDateTimeFragment(fragments, match) {
+    if (match[0].match(/^[a-zA-Z]+$/)) {
+        return;
+    }
     const num = parseNumberPattern(match[1]);
     const unit = TIME_UNIT_DICTIONARY[match[2].toLowerCase()];
     fragments[unit] = num;
diff --git a/src/locales/en/parsers/ENTimeUnitAgoFormatParser.ts b/src/locales/en/parsers/ENTimeUnitAgoFormatParser.ts
index a00d40cc..6f786f93 100644
--- a/src/locales/en/parsers/ENTimeUnitAgoFormatParser.ts
+++ b/src/locales/en/parsers/ENTimeUnitAgoFormatParser.ts
@@ -18,8 +18,10 @@ export default class ENTimeUnitAgoFormatParser extends AbstractParserWithWordBou
 
     innerExtract(context: ParsingContext, match: RegExpMatchArray) {
         const timeUnits = parseTimeUnits(match[1]);
+        if (!timeUnits) {
+            return null;
+        }
         const outputTimeUnits = reverseTimeUnits(timeUnits);
-
         return ParsingComponents.createRelativeFromReference(context.reference, outputTimeUnits);
     }
 }
diff --git a/src/locales/en/parsers/ENTimeUnitCasualRelativeFormatParser.ts b/src/locales/en/parsers/ENTimeUnitCasualRelativeFormatParser.ts
index 505e2596..f76c0c66 100644
--- a/src/locales/en/parsers/ENTimeUnitCasualRelativeFormatParser.ts
+++ b/src/locales/en/parsers/ENTimeUnitCasualRelativeFormatParser.ts
@@ -19,9 +19,12 @@ export default class ENTimeUnitCasualRelativeFormatParser extends AbstractParser
         return this.allowAbbreviations ? PATTERN : PATTERN_NO_ABBR;
     }
 
-    innerExtract(context: ParsingContext, match: RegExpMatchArray): ParsingComponents {
+    innerExtract(context: ParsingContext, match: RegExpMatchArray) {
         const prefix = match[1].toLowerCase();
         let timeUnits = parseTimeUnits(match[2]);
+        if (!timeUnits) {
+            return null;
+        }
         switch (prefix) {
             case "last":
             case "past":
@@ -29,7 +32,6 @@ export default class ENTimeUnitCasualRelativeFormatParser extends AbstractParser
                 timeUnits = reverseTimeUnits(timeUnits);
                 break;
         }
-
         return ParsingComponents.createRelativeFromReference(context.reference, timeUnits);
     }
 }
diff --git a/src/locales/en/parsers/ENTimeUnitLaterFormatParser.ts b/src/locales/en/parsers/ENTimeUnitLaterFormatParser.ts
index 91286951..7aff05a2 100644
--- a/src/locales/en/parsers/ENTimeUnitLaterFormatParser.ts
+++ b/src/locales/en/parsers/ENTimeUnitLaterFormatParser.ts
@@ -21,7 +21,10 @@ export default class ENTimeUnitLaterFormatParser extends AbstractParserWithWordB
     }
 
     innerExtract(context: ParsingContext, match: RegExpMatchArray) {
-        const fragments = parseTimeUnits(match[GROUP_NUM_TIMEUNITS]);
-        return ParsingComponents.createRelativeFromReference(context.reference, fragments);
+        const timeUnits = parseTimeUnits(match[GROUP_NUM_TIMEUNITS]);
+        if (!timeUnits) {
+            return null;
+        }
+        return ParsingComponents.createRelativeFromReference(context.reference, timeUnits);
     }
 }
diff --git a/src/locales/en/parsers/ENTimeUnitWithinFormatParser.ts b/src/locales/en/parsers/ENTimeUnitWithinFormatParser.ts
index 1ffea93b..1591aee4 100644
--- a/src/locales/en/parsers/ENTimeUnitWithinFormatParser.ts
+++ b/src/locales/en/parsers/ENTimeUnitWithinFormatParser.ts
@@ -33,13 +33,15 @@ export default class ENTimeUnitWithinFormatParser extends AbstractParserWithWord
         return context.option.forwardDate ? PATTERN_WITH_OPTIONAL_PREFIX : PATTERN_WITH_PREFIX;
     }
 
-    innerExtract(context: ParsingContext, match: RegExpMatchArray): ParsingComponents {
+    innerExtract(context: ParsingContext, match: RegExpMatchArray) {
         // Exclude "for the unit" phases, e.g. "for the year"
         if (match[0].match(/^for\s*the\s*\w+/)) {
             return null;
         }
-
         const timeUnits = parseTimeUnits(match[1]);
+        if (!timeUnits) {
+            return null;
+        }
         return ParsingComponents.createRelativeFromReference(context.reference, timeUnits);
     }
 }
diff --git a/test/en/en_time_units_ago.test.ts b/test/en/en_time_units_ago.test.ts
index 096900f6..58fae5cf 100644
--- a/test/en/en_time_units_ago.test.ts
+++ b/test/en/en_time_units_ago.test.ts
@@ -347,4 +347,7 @@ test("Test - Negative cases", function () {
     testUnexpectedResult(chrono, "15 hours 29 min");
     testUnexpectedResult(chrono, "a few hour");
     testUnexpectedResult(chrono, "5 days");
+
+    testUnexpectedResult(chrono, "am ago");
+    testUnexpectedResult(chrono, "them ago");
 });
diff --git a/test/en/en_time_units_casual_relative.test.ts b/test/en/en_time_units_casual_relative.test.ts
index 59107743..b9e2a6e6 100644
--- a/test/en/en_time_units_casual_relative.test.ts
+++ b/test/en/en_time_units_casual_relative.test.ts
@@ -164,4 +164,7 @@ test("Test - Negative cases", () => {
     testUnexpectedResult(chrono.casual, "1 m", new Date(2015, 7 - 1, 10, 12, 14));
     testUnexpectedResult(chrono.casual, "the day", new Date(2015, 7 - 1, 10, 12, 14));
     testUnexpectedResult(chrono.casual, "a day", new Date(2015, 7 - 1, 10, 12, 14));
+
+    testUnexpectedResult(chrono, "+am");
+    testUnexpectedResult(chrono, "+them");
 });
diff --git a/test/en/en_time_units_later.test.ts b/test/en/en_time_units_later.test.ts
index 31e4cf1a..fbb1a0f7 100644
--- a/test/en/en_time_units_later.test.ts
+++ b/test/en/en_time_units_later.test.ts
@@ -354,3 +354,7 @@ test("Test - Plus after reference", () => {
         expect(result.start.get("minute")).toBe(10);
     });
 });
+
+test("Test - Negative cases", () => {
+    testUnexpectedResult(chrono, "tell them later");
+});
diff --git a/test/en/en_time_units_within.test.ts b/test/en/en_time_units_within.test.ts
index d610b59f..703d9cfa 100644
--- a/test/en/en_time_units_within.test.ts
+++ b/test/en/en_time_units_within.test.ts
@@ -408,3 +408,8 @@ test("Test - Forward date option", () => {
         expect(result.start.get("day")).toBe(1);
     });
 });
+
+test("Test - Negative cases", () => {
+    testUnexpectedResult(chrono, "in am");
+    testUnexpectedResult(chrono, "in them");
+});