Martin, a McHugh employee, was injured at work in Maryland and received payments under the Maryland Workmen’s Compensation Law. If he had been injured in the District his compensation would have been larger. McHugh was bound by contract to “carry an excess compensation policy on his employees when they are working outside of the District of Columbia which shall give * * * additional compensation in Maryland and Virginia equal to that of the District of Columbia.” Martin brought this suit against McHugh for the amount of the excess compensation.

Defendant McHugh filed a complaint as third-party plaintiff against Michigan Mutual Liability Company, contending that McHugh’s contractual liability to plaintiff Martin was covered by the insurance McHugh was carrying in Michigan Mutual. The District Court ruled against this contention and entered summary judgment for both Martin and Michigan Mutual against McHugh. McHugh appeals.

We think Michigan Mutual’s “Comprehensive General Liability Policy” and “Contractual Liability Coverage Endorsement” are sufficiently ambiguous in respect to coverage to justify a trial in which the surrounding circumstances may be developed and the intentions of the parties determined.

Remanded.