diff --git a/src/cfnlint/data/schemas/extensions/aws_ecs_taskdefinition/fargate_cpu_memory.json b/src/cfnlint/data/schemas/extensions/aws_ecs_taskdefinition/fargate_cpu_memory.json
index 4f6f376241..d55d7ca69b 100644
--- a/src/cfnlint/data/schemas/extensions/aws_ecs_taskdefinition/fargate_cpu_memory.json
+++ b/src/cfnlint/data/schemas/extensions/aws_ecs_taskdefinition/fargate_cpu_memory.json
@@ -51,14 +51,23 @@
       }
      },
      "Memory": {
-      "enum": [
-       "0.5 GB",
-       "1 GB",
-       "2 GB",
-       "512",
-       "1024",
-       "2048"
-      ]
+      "else": {
+       "pattern": "^(0.5|1|2)\\s*(?i)GB$"
+      },
+      "if": {
+       "pattern": "^\\d+$",
+       "type": [
+        "integer",
+        "string"
+       ]
+      },
+      "then": {
+       "enum": [
+        512,
+        1024,
+        2048
+       ]
+      }
      }
     }
    },
diff --git a/src/cfnlint/helpers.py b/src/cfnlint/helpers.py
index 77c2283fb5..d728ec2c1d 100644
--- a/src/cfnlint/helpers.py
+++ b/src/cfnlint/helpers.py
@@ -136,7 +136,7 @@
 REGEX_DYN_REF_SSM_SECURE = re.compile(
     r"^.*{{resolve:ssm-secure:[a-zA-Z0-9_\.\-/]+(:\d+)?}}.*$"
 )
-REGEX_SUB_PARAMETERS = re.compile(r"\${([^!].*?)}")
+REGEX_SUB_PARAMETERS = re.compile(r"\${\s*([^!\s].*?)\s*}")
 
 FUNCTIONS = frozenset(
     [
diff --git a/test/unit/rules/functions/test_sub.py b/test/unit/rules/functions/test_sub.py
index 0e6c55c8e4..e3b813e2fa 100644
--- a/test/unit/rules/functions/test_sub.py
+++ b/test/unit/rules/functions/test_sub.py
@@ -162,6 +162,18 @@ def context(cfn):
             {"type": "string"},
             [],
         ),
+        (
+            "Valid Fn::Sub with a space and escape char",
+            {"Fn::Sub": "${ !Foo }"},
+            {"type": "string"},
+            [],
+        ),
+        (
+            "Valid Fn::Sub with a space and no escape char",
+            {"Fn::Sub": "${ AWS::AccountId }"},
+            {"type": "string"},
+            [],
+        ),
         (
             "Invalid Fn::Sub with a too to many elements",
             {"Fn::Sub": ["${foo}", {"foo": "bar"}, {}]},