diff --git a/c/qrcodegen.c b/c/qrcodegen.c
index 612409a..cf7cd64 100644
--- a/c/qrcodegen.c
+++ b/c/qrcodegen.c
@@ -345,6 +345,7 @@ testable int getNumRawDataModules(int ver) {
 		if (ver >= 7)
 			result -= 36;
 	}
+	assert(208 <= result && result <= 29648);
 	return result;
 }
 
diff --git a/cpp/QrCode.cpp b/cpp/QrCode.cpp
index 4c8bdfc..a6e2568 100644
--- a/cpp/QrCode.cpp
+++ b/cpp/QrCode.cpp
@@ -531,6 +531,8 @@ int QrCode::getNumRawDataModules(int ver) {
 		if (ver >= 7)
 			result -= 36;
 	}
+	if (!(208 <= result && result <= 29648))
+		throw std::logic_error("Assertion error");
 	return result;
 }
 
diff --git a/java/src/main/java/io/nayuki/qrcodegen/QrCode.java b/java/src/main/java/io/nayuki/qrcodegen/QrCode.java
index f7d8ab7..68c4f99 100644
--- a/java/src/main/java/io/nayuki/qrcodegen/QrCode.java
+++ b/java/src/main/java/io/nayuki/qrcodegen/QrCode.java
@@ -718,6 +718,7 @@ public final class QrCode {
 			if (ver >= 7)
 				result -= 6 * 3 * 2;  // Subtract version information
 		}
+		assert 208 <= result && result <= 29648;
 		return result;
 	}
 	
diff --git a/python/qrcodegen.py b/python/qrcodegen.py
index 6ada1aa..93c0e85 100644
--- a/python/qrcodegen.py
+++ b/python/qrcodegen.py
@@ -550,6 +550,7 @@ class QrCode(object):
 			result -= (25 * numalign - 10) * numalign - 55
 			if ver >= 7:
 				result -= 36
+		assert 208 <= result <= 29648
 		return result
 	
 	
diff --git a/rust/src/lib.rs b/rust/src/lib.rs
index 1c38e41..258761a 100644
--- a/rust/src/lib.rs
+++ b/rust/src/lib.rs
@@ -753,6 +753,7 @@ impl QrCode {
 				result -= 36;
 			}
 		}
+		assert!(208 <= result && result <= 29648);
 		result
 	}
 	
diff --git a/typescript-javascript/qrcodegen.ts b/typescript-javascript/qrcodegen.ts
index 00e7827..9b75c06 100644
--- a/typescript-javascript/qrcodegen.ts
+++ b/typescript-javascript/qrcodegen.ts
@@ -619,6 +619,8 @@ namespace qrcodegen {
 				if (ver >= 7)
 					result -= 36;
 			}
+			if (!(208 <= result && result <= 29648))
+				throw "Assertion error";
 			return result;
 		}