This error occurs when a version constraint string in your Terraform configuration uses incorrect syntax. Version constraints appear in required_version, required_providers blocks, and module version fields. Common causes include malformed operators, missing version numbers, empty strings, and unsupported syntax. The fix involves using proper version constraint operators and format.
Terraform requires version constraints to follow a specific syntax format. A version constraint is a string that specifies which versions of Terraform, providers, or modules are acceptable. When Terraform encounters a malformed constraint string, it cannot parse it and raises this error. Terraform validates version constraint syntax during the terraform init phase. The error means your configuration contains a version string that does not conform to Terraform's version constraint language. This typically happens with typos in operators, empty strings, or attempts to use unsupported syntax.
The error message should indicate which version constraint is malformed. Look for:
- required_version in the terraform block
- version in the required_providers block
- version in module blocks
Example of a properly structured terraform block:
terraform {
required_version = ">= 1.0"
required_providers {
aws = {
source = "hashicorp/aws"
version = "~> 5.0"
}
}
}Check your configuration files (.tf files) for the referenced field and note the exact constraint value.
Common mistakes and their fixes:
Wrong - Empty string:
required_version = ""Correct:
required_version = ">= 1.0"Wrong - Undefined value:
terraform {
required_providers {
aws = {
source = "hashicorp/aws"
version = undefined
}
}
}Correct:
terraform {
required_providers {
aws = {
source = "hashicorp/aws"
version = "~> 5.0"
}
}
}Terraform supports these version constraint operators:
| Operator | Meaning | Example |
|----------|---------|---------|
| = or none | Exact version | = 1.5.0 or 1.5.0 |
| != | Not equal | != 1.4.0 |
| > | Greater than | > 1.0 |
| >= | Greater than or equal | >= 1.5.0 |
| < | Less than | < 2.0 |
| <= | Less than or equal | <= 1.9.0 |
| ~> | Pessimistic (rightmost increments only) | ~> 1.5 allows 1.5.0-1.9.9 but not 2.0 |
Examples of valid constraints:
terraform {
required_version = ">= 1.0, < 2.0"
}
terraform {
required_providers {
aws = {
source = "hashicorp/aws"
version = "~> 5.15" # Allows 5.15.0 to 5.99.x
}
google = {
source = "hashicorp/google"
version = ">= 5.0, < 6.0"
}
}
}Version numbers must follow semantic versioning: MAJOR.MINOR.PATCH
Valid version numbers:
- 1.0.0
- 1.5 (patch defaults to .0)
- 1 (minor and patch default to .0)
Invalid version numbers:
- 1.0.0.0 (too many components)
- 1.x.0 (x is not valid, use comparison operators instead)
- latest (not supported, use constraint operators)
- v1.5.0 (remove the v prefix)
Correct ways to specify versions:
# Exact version
version = "= 1.5.0"
# Minimum version (common for modules)
version = ">= 1.0.0"
# Version range
version = ">= 1.5.0, < 2.0.0"
# Pessimistic constraint (recommended for providers)
version = "~> 1.5"After fixing your version constraints, validate your configuration:
terraform validateIf validation passes, you can proceed to initialize:
terraform initIf terraform validate still fails, check the error message againโit will pinpoint which constraint is still invalid. Common issues to double-check:
- No leading/trailing spaces in version strings
- All quotes are properly closed
- Operators are spelled correctly (~> not ~>> or ~, >=, not >==)
- Version numbers use dots, not commas between components (1.5.0 not 1,5,0)
When using modules, you can specify version constraints. Ensure the syntax is correct:
Wrong:
module "vpc" {
source = "terraform-aws-modules/vpc/aws"
version = "" # Empty constraint
}Correct:
module "vpc" {
source = "terraform-aws-modules/vpc/aws"
version = "~> 5.0" # Allows 5.x.x
}For local modules (relative paths), you typically omit the version constraint:
module "custom" {
source = "./modules/custom"
# No version constraint for local modules
}Registry modules (terraform-aws-modules, etc.) should have version constraints to ensure stability.
If you see the error alongside an invalid source URL, ensure the provider source is correct:
Wrong:
terraform {
required_providers {
aws = {
source = "" # Empty source
version = "~> 5.0"
}
}
}Correct:
terraform {
required_providers {
aws = {
source = "hashicorp/aws" # namespace/type format
version = "~> 5.0"
}
}
}Use the [Terraform Registry](https://registry.terraform.io) to find correct provider sources and compatible versions.
Pre-release Versions: If you need to use a pre-release version (e.g., 1.5.0-beta), you must specify the exact version with the = operator. Pre-release versions are not matched by >, >=, <, <=, or ~> operators.
required_version = "= 1.5.0-beta1"Combining Multiple Constraints: You can combine multiple constraint conditions with commas. All conditions must be satisfied:
required_version = ">= 1.0, < 2.0, != 1.5.0" # Allows 1.x except 1.5.0Version Pinning Best Practices: For production, pin both major and minor versions using pessimistic constraint:
# Good - allows patch updates only
required_version = "~> 1.5" # 1.5.0 to 1.9.x
# Also good - explicit range
required_version = ">= 1.5.0, < 1.6.0"
# Less safe - too permissive
required_version = ">= 1.0" # Could jump to 2.0 unexpectedlyFor Modules: Reusable modules should use loose constraints (minimum version only) to give callers flexibility:
# In a reusable module
terraform {
required_version = ">= 1.0"
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