Thomas Mutryn
Analyst · this time, I would like to turn the conference call over to Dave Dragics, Senior Vice President of Investor Relations for CACI International. Please go ahead, sir
All right, thank you, Ken, and good morning, everyone. Let's go to Slide #6.
Our first quarter revenue was $1.09 billion, 1.2% greater than the first quarter last year with 1.1% organic growth. Net income for the quarter was $42 million, up 15% driven by tax benefits related to equity-based compensation.
Our adjusted net income, which excludes several non-cash expenses, was $56.7 million for the quarter, 35% greater than our GAAP net income.
Operating income in the quarter was down a bit. Gross margin dollars increased but indirect expenses grew modestly at 1.5%, driven by spending related to various growth initiatives and investment in systems to drive future efficiencies. Let me discuss the mechanics of the tax benefit in the quarter. A significant portion of executive compensation is tied to our equity, to align compensation with shareholder interest. In FY '16, we adopted an accounting rule related to share-based payments. Previously, differences between the value of tax deductions from when share-based compensation was initially recorded and when the awards vest were treated as balance sheet adjustments.
The new guidance specifies that the differences flow through the income statement. Restricted stock units are typically granted annually in the September quarter, invest at the end of year 3 and 4. Given the material increase in our stock price, the units divested this September generated significantly higher tax deductions than initially reported. This resulted in approximately $6 million of tax savings, all of which is reflected in this quarter's effective rate.
Slide 7 please. We generated $80 million of operating cash flow in the quarter with days sales outstanding at 64 days, up from 59 days at the end of June, due to typical fluctuations in collections. Accounts payable also increased due to normal payment timing. Operating cash flow grew 38% compared to last year and it was almost 190% of our net income. In the absence of compelling acquisitions, we have been using our cash flow to retire debt. Net debt at the end of September was $1.1 billion. And our net debt to trailing 12-month EBITDA leverage ratio was now at 3.0x, down from 3.9x following the NSS acquisition.
Slide 8 please. And lastly, As Ken mentioned, we are raising our upper and lower net income guidance range by $6 billion to reflect the equity-based compensation tax benefit, with corresponding increases to the earnings per share range. We now expect our full-year effective tax rate to be 34.5% and we are on track to realize our annual organic growth and margin expansion goals, which Ken articulated.
With that, here's John to provide operational highlights.